Add Splitter VFD to library.

* "Simultaneous and equivalent" Read-Write and Write-Only channels for
  file I/O.
* Only supports drivers with the H5FD_FEAT_DEFAULT_VFD_COMPATIBLE flag for
  now, preventing issues with multi-file drivers.

Add Mirror VFD to library.

* Write-only operations over a network.
* Uses TCP/IP sockets.
* Server and auxiliary server-shutdown programs provided in a new directory,
  `utils/mirror_vfd`.
* Automated testing via loopback ("remote" of localhost).

13 files changed, 5011 insertions, 557 deletions

diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 2594477..cba1d3a 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -211,6 +211,11 @@ set (cache_image_SOURCES
     ${HDF5_TEST_SOURCE_DIR}/genall5.c
 )
 
+set(mirror_vfd_SOURCES
+    ${HDF5_TEST_SOURCE_DIR}/mirror_vfd.c
+    ${HDF5_TEST_SOURCE_DIR}/genall5.c
+)
+
 set (ttsafe_SOURCES
     ${HDF5_TEST_SOURCE_DIR}/ttsafe.c
     ${HDF5_TEST_SOURCE_DIR}/ttsafe_dcreate.c
@@ -273,6 +278,7 @@ set (H5_TESTS
     ros3
     s3comms
     hdfs
+    mirror_vfd
     ntypes
     dangle
     dtransform
@@ -310,6 +316,7 @@ set (H5_TESTS_MULTIPLE
     testhdf5
     cache_image
     ttsafe
+    mirror_vfd
 )
 # Only build single source tests here
 foreach (h5_test ${H5_TESTS})
@@ -389,6 +396,18 @@ else ()
 endif ()
 set_target_properties (ttsafe PROPERTIES FOLDER test)
 
+#-- Adding test for mirror_vfd
+add_executable (mirror_vfd ${mirror_vfd_SOURCES})
+target_include_directories (mirror_vfd PRIVATE "${HDF5_SRC_DIR};${HDF5_BINARY_DIR};$<$<BOOL:${HDF5_ENABLE_PARALLEL}>:${MPI_C_INCLUDE_DIRS}>")
+if (NOT BUILD_SHARED_LIBS)
+  TARGET_C_PROPERTIES (mirror_vfd STATIC)
+  target_link_libraries (mirror_vfd PRIVATE ${HDF5_TEST_LIB_TARGET})
+else ()
+  TARGET_C_PROPERTIES (mirror_vfd SHARED)
+  target_link_libraries (mirror_vfd PRIVATE ${HDF5_TEST_LIBSH_TARGET})
+endif ()
+set_target_properties (mirror_vfd PROPERTIES FOLDER test)
+
 ##############################################################################
 ###           A D D I T I O N A L   T E S T S                              ###
 ##############################################################################
diff --git a/test/CMakeTests.cmake b/test/CMakeTests.cmake
index b7eaa56..c73aeda 100644
--- a/test/CMakeTests.cmake
+++ b/test/CMakeTests.cmake
@@ -446,6 +446,10 @@ set (test_CLEANFILES
     vds_swmr_src_*.h5
     tmp_vds_env/vds_src_2.h5
     direct_chunk.h5
+    splitter*.h5
+    splitter.log
+    mirror_rw/*
+    mirror_wo/*
     native_vol_test.h5
 )
 
diff --git a/test/Makefile.am b/test/Makefile.am
index dd0a579..6bea16a 100644
--- a/test/Makefile.am
+++ b/test/Makefile.am
@@ -33,9 +33,11 @@ AM_CPPFLAGS+=-I$(top_srcdir)/src -I$(top_builddir)/src
 #       testvdsswmr.sh: vds_swmr*
 #       testabort_fail.sh: filenotclosed.c and del_many_dense_attrs.c
 #       test_filter_plugin.sh: filter_plugin.c
+#       test_mirror.sh: mirror_vfd ../utils/mirror_vfd/*
 #       test_usecases.sh: use_append_chunk, use_append_mchunks, use_disable_mdc_flushes
 TEST_SCRIPT = testerror.sh testlibinfo.sh testcheck_version.sh testlinks_env.sh testexternal_env.sh \
-    testswmr.sh testvds_env.sh testvdsswmr.sh testflushrefresh.sh test_usecases.sh testabort_fail.sh
+    testswmr.sh testvds_env.sh testvdsswmr.sh testflushrefresh.sh test_usecases.sh testabort_fail.sh \
+    test_mirror.sh
 SCRIPT_DEPEND = error_test$(EXEEXT) err_compat$(EXEEXT) links_env$(EXEEXT) \
     external_env$(EXEEXT) filenotclosed$(EXEEXT) del_many_dense_attrs$(EXEEXT) \
     flushrefresh$(EXEEXT) use_append_chunk$(EXEEXT) use_append_mchunks$(EXEEXT) use_disable_mdc_flushes$(EXEEXT) \
@@ -78,16 +80,18 @@ TEST_PROG= testhdf5 \
 # swmr_* files (besides swmr.c) are used by testswmr.sh.
 # vds_swmr_* files are used by testvdsswmr.sh
 # vds_env is used by testvds_env.sh
+# mirror_vfd is used by test_mirror.sh
 # 'make check' doesn't run them directly, so they are not included in TEST_PROG.
 # Also build testmeta, which is used for timings test.  It builds quickly,
 # and this lets automake keep all its test programs in one place.
 check_PROGRAMS=$(TEST_PROG) error_test err_compat tcheck_version \
     testmeta accum_swmr_reader atomic_writer atomic_reader external_env \
     links_env filenotclosed del_many_dense_attrs flushrefresh \
-    use_append_chunk use_append_mchunks use_disable_mdc_flushes \
+    use_append_chunk use_append_chunk_mirror use_append_mchunks use_disable_mdc_flushes \
     swmr_generator swmr_start_write swmr_reader swmr_writer swmr_remove_reader \
     swmr_remove_writer swmr_addrem_writer swmr_sparse_reader swmr_sparse_writer \
-    swmr_check_compat_vfd vds_env vds_swmr_gen vds_swmr_reader vds_swmr_writer
+    swmr_check_compat_vfd vds_env vds_swmr_gen vds_swmr_reader vds_swmr_writer \
+    mirror_vfd
 if HAVE_SHARED_CONDITIONAL
   check_PROGRAMS+= filter_plugin vol_plugin
 endif
@@ -144,6 +148,7 @@ LDADD=libh5test.la $(LIBHDF5)
 ttsafe_SOURCES=ttsafe.c ttsafe_dcreate.c ttsafe_error.c ttsafe_cancel.c       \
                ttsafe_acreate.c
 cache_image_SOURCES=cache_image.c genall5.c
+mirror_vfd_SOURCES=mirror_vfd.c genall5.c
 
 VFD_LIST = sec2 stdio core core_paged split multi family
 if DIRECT_VFD_CONDITIONAL
@@ -213,7 +218,8 @@ CHECK_CLEANFILES+=accum.h5 cmpd_dset.h5 compact_dataset.h5 dataset.h5 dset_offse
     flushrefresh_VERIFICATION_DONE atomic_data accum_swmr_big.h5 ohdr_swmr.h5 \
     test_swmr*.h5 cache_logging.h5 cache_logging.out vds_swmr.h5 vds_swmr_src_*.h5 \
     swmr[0-2].h5 swmr_writer.out swmr_writer.log.* swmr_reader.out.* swmr_reader.log.* \
-    tbogus.h5.copy cache_image_test.h5 direct_chunk.h5 native_vol_test.h5
+    tbogus.h5.copy cache_image_test.h5 direct_chunk.h5 native_vol_test.h5 \
+    splitter*.h5 splitter.log
 
 # Sources for testhdf5 executable
 testhdf5_SOURCES=testhdf5.c tarray.c tattr.c tchecksum.c tconfig.c tfile.c \
@@ -223,12 +229,13 @@ testhdf5_SOURCES=testhdf5.c tarray.c tattr.c tchecksum.c tconfig.c tfile.c \
 
 # Sources for Use Cases
 use_append_chunk_SOURCES=use_append_chunk.c use_common.c
+use_append_chunk_mirror_SOURCES=use_append_chunk_mirror.c use_common.c
 use_append_mchunks_SOURCES=use_append_mchunks.c use_common.c
 use_disable_mdc_flushes_SOURCES=use_disable_mdc_flushes.c
 
 # Temporary files.
 DISTCLEANFILES=testerror.sh testlibinfo.sh testcheck_version.sh testlinks_env.sh test_filter_plugin.sh \
-    testexternal_env.sh testswmr.sh testvds_env.sh testvdsswmr.sh test_usecases.sh testflushrefresh.sh testabort_fail.sh \
-	test_vol_plugin.sh
+    testexternal_env.sh testswmr.sh testvds_env.sh testvdsswmr.sh test_usecases.sh testflushrefresh.sh \
+    testabort_fail.sh test_vol_plugin.sh test_mirror.sh
 
 include $(top_srcdir)/config/conclude.am
diff --git a/test/h5test.c b/test/h5test.c
index 03731c6..e7d91b6 100644
--- a/test/h5test.c
+++ b/test/h5test.c
@@ -2043,6 +2043,80 @@ h5_get_version_string(H5F_libver_t libver)
 } /* end of h5_get_version_string */
 
 /*-------------------------------------------------------------------------
+ * Function:    h5_compare_file_bytes()
+ *
+ * Purpose:     Helper function to compare two files byte-for-byte.
+ *
+ * Return:      Success:  0, if files are identical
+ *              Failure: -1, if files differ
+ *
+ * Programmer:  Binh-Minh Ribler
+ *              October, 2018
+ *-------------------------------------------------------------------------
+ */
+int
+h5_compare_file_bytes(char *f1name, char *f2name)
+{
+    FILE    *f1ptr = NULL;  /* two file pointers */
+    FILE    *f2ptr = NULL;
+    hsize_t  f1size = 0; /* size of the files */
+    hsize_t  f2size = 0;
+    char     f1char = 0; /* one char from each file */
+    char     f2char = 0;
+    hsize_t  ii = 0;
+    int      ret_value = 0; /* for error handling */
+
+    /* Open files for reading */
+    f1ptr = fopen(f1name, "r");
+    if (f1ptr == NULL) {
+        HDfprintf(stderr, "Unable to fopen() %s\n", f1name);
+        ret_value = -1;
+        goto done;
+    }
+    f2ptr = fopen(f2name, "r");
+    if (f2ptr == NULL) {
+        HDfprintf(stderr, "Unable to fopen() %s\n", f2name);
+        ret_value = -1;
+        goto done;
+    }
+
+    /* Get the file sizes and verify that they equal */
+    fseek(f1ptr , 0 , SEEK_END);
+    f1size = ftell(f1ptr);
+
+    fseek(f2ptr , 0 , SEEK_END);
+    f2size = ftell(f2ptr);
+
+    if (f1size != f2size) {
+        HDfprintf(stderr, "Files differ in size, %llu vs. %llu\n", f1size, f2size);
+        ret_value = -1;
+        goto done;
+    }
+
+    /* Compare each byte and fail if a difference is found */
+    rewind(f1ptr);
+    rewind(f2ptr);
+    for (ii = 0; ii < f1size; ii++) {
+        fread(&f1char, 1, 1, f1ptr);
+        fread(&f2char, 1, 1, f2ptr);
+        if (f1char != f2char) {
+            HDfprintf(stderr, "Mismatch @ 0x%llX: 0x%X != 0x%X\n", ii, f1char, f2char);
+            ret_value = -1;
+            goto done;
+        }
+    }
+
+done:
+    if (f1ptr) {
+        fclose(f1ptr);
+    }
+    if (f2ptr) {
+        fclose(f2ptr);
+    }
+    return(ret_value);
+} /* end h5_compare_file_bytes() */
+
+/*-------------------------------------------------------------------------
  * Function:    H5_get_srcdir_filename
  *
  * Purpose:     Append the test file name to the srcdir path and return the whole string
@@ -2094,3 +2168,4 @@ const char *H5_get_srcdir(void)
     else
         return(NULL);
 } /* end H5_get_srcdir() */
+
diff --git a/test/h5test.h b/test/h5test.h
index e67e559..39ec9d7 100644
--- a/test/h5test.h
+++ b/test/h5test.h
@@ -150,6 +150,7 @@ H5TEST_DLL herr_t h5_verify_cached_stabs(const char *base_name[], hid_t fapl);
 H5TEST_DLL H5FD_class_t *h5_get_dummy_vfd_class(void);
 H5TEST_DLL H5VL_class_t *h5_get_dummy_vol_class(void);
 H5TEST_DLL const char *h5_get_version_string(H5F_libver_t libver);
+H5TEST_DLL int h5_compare_file_bytes(char *fname1, char *fname2);
 
 /* Functions that will replace components of a FAPL */
 H5TEST_DLL herr_t h5_get_vfd_fapl(hid_t fapl_id);
diff --git a/test/mirror_vfd.c b/test/mirror_vfd.c
new file mode 100644
index 0000000..00902dd
--- /dev/null
+++ b/test/mirror_vfd.c
@@ -0,0 +1,2736 @@
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
+ * Copyright by The HDF Group.                                               *
+ * All rights reserved.                                                      *
+ *                                                                           *
+ * This file is part of HDF5.  The full HDF5 copyright notice, including     *
+ * terms governing use, modification, and redistribution, is contained in    *
+ * the COPYING file, which can be found at the root of the source code       *
+ * distribution tree, or in https://support.hdfgroup.org/ftp/HDF5/releases.  *
+ * If you do not have access to either file, you may request a copy from     *
+ * help@hdfgroup.org.                                                        *
+ * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+/*
+ * Purpose: Test the Mirror VFD functionality.
+ */
+
+/* WARNING: The use of realpath() is probably system-dependent, as are
+ * other things here such as the socket calls.
+ * Notable to realpath() in particular is the use of "PATH_MAX", which
+ * apparently has some major potential issues if paths are abused.
+ * http://insanecoding.blogspot.com/2007/11/pathmax-simply-isnt.html
+ * so BE CAREFUL about the paths we throw around?
+ */
+
+#include "h5test.h"
+#include "cache_common.h"
+#include "genall5.h"
+
+#ifdef H5_HAVE_MIRROR_VFD
+
+/* For future consideration, IP address and port number might be
+ * environment variables?
+ */
+#define SERVER_IP_ADDRESS "127.0.0.1"
+
+/* Primary listening port on server. */
+#define SERVER_HANDSHAKE_PORT 3000
+
+#define DATABUFFER_SIZE 128
+#define DSET_NAME_LEN   16
+
+/* Parameters for the "large chunked dataset" writing */
+#define MAX_DSET_COUNT 255
+#define DSET_DIM        32
+#define CHUNK_DIM        8
+
+#define CONCURRENT_COUNT 3 /* Number of files in concurrent test */
+
+/* Macro: LOGPRINT()
+ * Prints logging and debugging messages to the output stream based
+ * on the level of verbosity.
+ *     0 : no logging
+ *     1 : errors only
+ *     2 : details
+ *     3 : all
+ */
+#define DEFAULT_VERBOSITY 1
+static unsigned int g_verbosity = DEFAULT_VERBOSITY;
+
+/* Macro for selective debug printing / logging */
+#define LOGPRINT(lvl, ...)                  \
+do {                                        \
+    if ((lvl) <= g_verbosity) {             \
+        fprintf(g_log_stream, __VA_ARGS__); \
+        fflush(g_log_stream);               \
+    }                                       \
+} while (0)
+
+#define MIRROR_RW_DIR "mirror_rw/"
+#define MIRROR_WO_DIR "mirror_wo/"
+
+/* String buffer for error messages */
+#define MIRR_MESG_SIZE 128
+static char mesg[MIRR_MESG_SIZE + 1];
+
+/* Convenience structure for passing file names via helper functions.
+ */
+struct mirrortest_filenames {
+    char rw[H5FD_SPLITTER_PATH_MAX+1];
+    char wo[H5FD_SPLITTER_PATH_MAX+1];
+    char log[H5FD_SPLITTER_PATH_MAX+1];
+};
+
+static FILE *g_log_stream = NULL; /* initialized at runtime */
+
+static herr_t _verify_datasets(unsigned min_dset, unsigned max_dset,
+        hid_t *filespace_id, hid_t *dataset_id, hid_t memspace_id);
+
+static herr_t _create_chunking_ids(hid_t file_id, unsigned min_dset,
+        unsigned max_dset, hsize_t *chunk_dims, hsize_t *dset_dims,
+        hid_t *dataspace_ids, hid_t *filespace_ids, hid_t *dataset_ids,
+        hid_t *memspace_id);
+
+static herr_t _close_chunking_ids(unsigned min_dset, unsigned max_dset,
+        hid_t *dataspace_ids, hid_t *filespace_ids, hid_t *dataset_ids,
+        hid_t *memspace_id);
+
+static herr_t _populate_filepath(const char *dirname, const char *_basename,
+        hid_t fapl_id, char *path_out, hbool_t h5suffix);
+
+static hid_t create_mirroring_split_fapl(const char *_basename,
+        struct mirrortest_filenames *names);
+
+
+/* ----------------------------------------------------------------------------
+ * Function:   _populate_filepath
+ *
+ * Purpose:    Given a directory name and a base name, concatenate the two and
+ *             run h5fixname() to get the "actual" path to the intented target.
+ *             `h5suffix' should be FALSE to keep the base name unaltered;
+ *             TRUE will append the '.h5' h5suffix to the basename...
+ *             FALSE -> h5fixname_no_suffix(), TRUE -> h5fixname()
+ *             <h5fixname_prefix> / <dirname> / <_basename> <h5prefix?>
+ *
+ * Programmer: Jacob Smith
+ *             2019-08-16
+ * ----------------------------------------------------------------------------
+ */
+static herr_t
+_populate_filepath(const char *dirname, const char *_basename, hid_t fapl_id,
+                   char *path_out, hbool_t h5suffix)
+{
+    char _path[H5FD_SPLITTER_PATH_MAX];
+
+    if ((_basename == NULL) ||
+        (*_basename == 0)   ||
+        (dirname == NULL)   ||
+        (*dirname == 0)     ||
+        (path_out == NULL))
+    {
+        TEST_ERROR;
+    }
+
+    if (HDsnprintf(_path, H5FD_SPLITTER_PATH_MAX, "%s%s%s", dirname,
+            (dirname[strlen(dirname)] == '/') ? "" : "/", /* slash iff needed */
+            _basename)
+        > H5FD_SPLITTER_PATH_MAX)
+    {
+        TEST_ERROR;
+    }
+
+    if (h5suffix == TRUE) {
+        if (h5_fixname(_path, fapl_id, path_out,
+                H5FD_SPLITTER_PATH_MAX)
+            == NULL)
+        {
+            TEST_ERROR;
+        }
+    }
+    else {
+        if (h5_fixname_no_suffix(_path, fapl_id, path_out,
+                H5FD_SPLITTER_PATH_MAX)
+            == NULL)
+        {
+            TEST_ERROR;
+        }
+    }
+
+    return SUCCEED;
+
+error:
+    return FAIL;
+} /* end _populate_filepath() */
+
+
+/* ---------------------------------------------------------------------------
+ * Function:    build_paths
+ *
+ * Purpose:     Convenience function to create the three file paths used in
+ *              most mirror tests.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ * Programmer:  Jacob Smith
+ *              2019-08-16
+ * ---------------------------------------------------------------------------
+ */
+static herr_t
+build_paths(
+        const char                  *_basename,
+        H5FD_splitter_vfd_config_t  *splitter_config,
+        struct mirrortest_filenames *names)
+{
+    char baselogname[H5FD_SPLITTER_PATH_MAX];
+
+    if (_populate_filepath(MIRROR_RW_DIR, _basename,
+            splitter_config->rw_fapl_id, names->rw, TRUE)
+        == FAIL)
+    {
+        TEST_ERROR;
+    }
+
+    if (_populate_filepath(MIRROR_WO_DIR, _basename,
+            splitter_config->wo_fapl_id, names->wo, TRUE)
+        == FAIL)
+    {
+        TEST_ERROR;
+    }
+
+    if (_basename == NULL || *_basename == 0)
+        return FAIL;
+    if (HDsnprintf(baselogname, H5FD_SPLITTER_PATH_MAX, "%s_err.log",
+            _basename)
+        > H5FD_SPLITTER_PATH_MAX)
+    {
+        TEST_ERROR;
+    }
+
+    if (_populate_filepath(MIRROR_WO_DIR, baselogname,
+            splitter_config->wo_fapl_id, names->log, FALSE)
+        == FAIL)
+    {
+        TEST_ERROR;
+    }
+
+    return SUCCEED;
+
+error:
+    return FAIL;
+} /* end build_paths() */
+
+
+/* ---------------------------------------------------------------------------
+ * Function:    test_fapl_configuration
+ *
+ * Purpose:     Test FAPL configuration and examination.
+ *
+ * Return:      Success: 0
+ *              Failure: -1
+ *
+ * Programmer:  Jacob Smith
+ *              2019-03-12
+ * ---------------------------------------------------------------------------
+ */
+static int
+test_fapl_configuration(void)
+{
+    hid_t fapl_id;
+    H5FD_mirror_fapl_t mirror_conf = {
+        H5FD_MIRROR_FAPL_MAGIC,          /* magic */
+        H5FD_MIRROR_CURR_FAPL_T_VERSION, /* version */
+        SERVER_HANDSHAKE_PORT,           /* handhake_port */
+        SERVER_IP_ADDRESS,               /* remote_ip "IP address" */
+    };
+    H5FD_mirror_fapl_t fa_out = {0, 0, 0, ""};
+
+    TESTING("Mirror fapl configuration (set/get)");
+
+    fapl_id = H5Pcreate(H5P_FILE_ACCESS);
+    if (H5I_INVALID_HID == fapl_id) {
+        TEST_ERROR;
+    }
+
+    if (H5Pset_fapl_mirror(fapl_id, &mirror_conf) == FAIL) {
+        TEST_ERROR;
+    }
+
+    if (H5Pget_fapl_mirror(fapl_id, &fa_out) == FAIL) {
+        TEST_ERROR;
+    }
+    if (H5FD_MIRROR_FAPL_MAGIC != fa_out.magic) {
+        TEST_ERROR;
+    }
+    if (H5FD_MIRROR_CURR_FAPL_T_VERSION != fa_out.version) {
+        TEST_ERROR;
+    }
+    if (SERVER_HANDSHAKE_PORT != fa_out.handshake_port) {
+        TEST_ERROR;
+    }
+    if (HDstrncmp(SERVER_IP_ADDRESS, (const char *)fa_out.remote_ip,
+            H5FD_MIRROR_MAX_IP_LEN))
+    {
+        TEST_ERROR;
+    }
+
+    if (H5Pclose(fapl_id) == FAIL) {
+        TEST_ERROR;
+    }
+
+    PASSED();
+    return 0;
+
+error:
+    if (H5I_INVALID_HID != fapl_id) {
+        (void)H5Pclose(fapl_id);
+    }
+    return -1;
+} /* end test_fapl_configuration() */
+
+
+
+#define PRINT_BUFFER_DIFF(act, exp, len) do {                                 \
+    size_t _x = 0;                                                            \
+    while ((act)[_x] == (exp)[_x]) {                                          \
+        _x++;                                                                 \
+    }                                                                         \
+    if (_x != (len)) {                                                        \
+        size_t _y = 0;                                                        \
+        HDprintf("First bytes differ at %zu\n", _x);                          \
+        HDprintf("exp  ");                                                    \
+        for (_y = _x; _y < (len); _y++) {                                     \
+            HDprintf("%02X", (unsigned char)(exp)[_y]);                       \
+        }                                                                     \
+        HDprintf("\nact  ");                                                  \
+        for (_y = _x; _y < (len); _y++) {                                     \
+            HDprintf("%02X", (unsigned char)(act)[_y]);                       \
+        }                                                                     \
+        HDprintf("\n");                                                       \
+    }                                                                         \
+} while (0); /* end PRINT_BUFFER_DIFF */
+
+
+/* ---------------------------------------------------------------------------
+ * Function:    test_xmit_encode_decode
+ *
+ * Purpose:     Test byte-encoding operations for network transport.
+ *
+ * Return:      Success: 0
+ *              Failure: -1
+ *
+ * Programmer:  Jacob Smith
+ *              2020-02-02
+ * ---------------------------------------------------------------------------
+ */
+static int
+test_xmit_encode_decode(void)
+{
+    H5FD_mirror_xmit_t xmit_mock; /* re-used header in various xmit tests */
+
+    TESTING("Mirror encode/decode of xmit elements");
+
+    /* Set bogus values matching expected; encoding doesn't care
+     * Use sequential values to easily generate the expected buffer with a
+     * for loop.
+     */
+    xmit_mock.magic = 0x00010203;
+    xmit_mock.version = 0x04;
+    xmit_mock.session_token = 0x05060708;
+    xmit_mock.xmit_count = 0x090A0B0C;
+    xmit_mock.op = 0x0D;
+
+    /* Test uint8_t encode/decode
+     */
+    do {
+        unsigned char buf[8];
+        unsigned char expected[8];
+        const uint8_t v = 200;
+        unsigned char out = 0;
+
+        /* Start of buffer uint8_t
+         */
+        HDbzero(buf, 8);
+        HDbzero(expected, 8);
+        expected[0] = 200;
+        out = 0;
+        if (H5FD__mirror_xmit_encode_uint8(buf, v) != 1) {
+            TEST_ERROR;
+        }
+        if (HDmemcmp(buf, expected, 8) != 0) {
+            PRINT_BUFFER_DIFF(buf, expected, 8);
+            TEST_ERROR;
+        }
+        if (H5FD__mirror_xmit_decode_uint8(&out, buf) != 1) {
+            TEST_ERROR;
+        }
+        if (v != out) {
+            TEST_ERROR;
+        }
+
+        /* Middle of buffer uint8_t
+         */
+        HDbzero(buf, 8);
+        HDbzero(expected, 8);
+        expected[3] = v;
+        out = 0;
+        if (H5FD__mirror_xmit_encode_uint8((buf+3), v) != 1) {
+            TEST_ERROR;
+        }
+        if (HDmemcmp(buf, expected, 8) != 0) {
+            PRINT_BUFFER_DIFF(buf, expected, 8);
+            TEST_ERROR;
+        }
+        if (H5FD__mirror_xmit_decode_uint8(&out, (buf+3)) != 1) {
+            TEST_ERROR;
+        }
+        if (v != out) {
+            TEST_ERROR;
+        }
+
+        /* End of buffer uint8_t
+         */
+        HDbzero(buf, 8);
+        HDbzero(expected, 8);
+        expected[7] = v;
+        out = 0;
+        if (H5FD__mirror_xmit_encode_uint8((buf+7), v) != 1) {
+            TEST_ERROR;
+        }
+        if (HDmemcmp(buf, expected, 8) != 0) {
+            PRINT_BUFFER_DIFF(buf, expected, 8);
+            TEST_ERROR;
+        }
+        if (H5FD__mirror_xmit_decode_uint8(&out, (buf+7)) != 1) {
+            TEST_ERROR;
+        }
+        if (v != out) {
+            TEST_ERROR;
+        }
+
+    } while (0); /* end uint8_t en/decode */
+
+    /* Test uint16_t encode/decode
+     */
+    do {
+        unsigned char  buf[8];
+        unsigned char  expected[8];
+        const uint16_t v = 0x8F02;
+        uint16_t out = 0;
+
+        /* Start of buffer uint16_t
+         */
+        HDbzero(buf, 8);
+        HDbzero(expected, 8);
+        expected[0] = 0x8F;
+        expected[1] = 0x02;
+        out = 0;
+        if (H5FD__mirror_xmit_encode_uint16(buf, v) != 2) {
+            TEST_ERROR;
+        }
+        if (HDmemcmp(buf, expected, 8) != 0) {
+            PRINT_BUFFER_DIFF(buf, expected, 8);
+            TEST_ERROR;
+        }
+        if (H5FD__mirror_xmit_decode_uint16(&out, buf) != 2) {
+            TEST_ERROR;
+        }
+        if (out != v) {
+            TEST_ERROR;
+        }
+
+        /* Middle of buffer uint16_t
+         */
+        HDbzero(buf, 8);
+        HDbzero(expected, 8);
+        expected[3] = 0x8F;
+        expected[4] = 0x02;
+        out = 0;
+        if (H5FD__mirror_xmit_encode_uint16((buf+3), v) != 2) {
+            TEST_ERROR;
+        }
+        if (HDmemcmp(buf, expected, 8) != 0) {
+            PRINT_BUFFER_DIFF(buf, expected, 8);
+            TEST_ERROR;
+        }
+        if (H5FD__mirror_xmit_decode_uint16(&out, (buf+3)) != 2) {
+            TEST_ERROR;
+        }
+        if (out != v) {
+            TEST_ERROR;
+        }
+        /* slice */
+        if (H5FD__mirror_xmit_decode_uint16(&out, (buf+4)) != 2) {
+            TEST_ERROR;
+        }
+        if (out != 0x0200) {
+            TEST_ERROR;
+        }
+
+        /* End of buffer uint16_t
+         */
+        HDbzero(buf, 8);
+        HDbzero(expected, 8);
+        expected[6] = 0x8F;
+        expected[7] = 0x02;
+        out = 0;
+        if (H5FD__mirror_xmit_encode_uint16((buf+6), v) != 2) {
+            TEST_ERROR;
+        }
+        if (HDmemcmp(buf, expected, 8) != 0) {
+            PRINT_BUFFER_DIFF(buf, expected, 8);
+            TEST_ERROR;
+        }
+        if (H5FD__mirror_xmit_decode_uint16(&out, (buf+6)) != 2) {
+            TEST_ERROR;
+        }
+        if (out != v) {
+            TEST_ERROR;
+        }
+
+    } while (0); /* end uint16_t en/decode */
+
+    /* Test uint32_t encode/decode
+     */
+    do {
+        unsigned char  buf[8];
+        unsigned char  expected[8];
+        const uint32_t v = 0x8F020048;
+        uint32_t out = 0;
+
+        /* Start of buffer uint32_t
+         */
+        HDbzero(buf, 8);
+        HDbzero(expected, 8);
+        expected[0] = 0x8F;
+        expected[1] = 0x02;
+        expected[2] = 0x00;
+        expected[3] = 0x48;
+        out = 0;
+        if (H5FD__mirror_xmit_encode_uint32(buf, v) != 4) {
+            TEST_ERROR;
+        }
+        if (HDmemcmp(buf, expected, 8) != 0) {
+            PRINT_BUFFER_DIFF(buf, expected, 8);
+            TEST_ERROR;
+        }
+        if (H5FD__mirror_xmit_decode_uint32(&out, buf) != 4) {
+            TEST_ERROR;
+        }
+        if (out != v) {
+            TEST_ERROR;
+        }
+
+        /* Middle of buffer uint32_t
+         */
+        HDbzero(buf, 8);
+        HDbzero(expected, 8);
+        expected[3] = 0x8F;
+        expected[4] = 0x02;
+        expected[5] = 0x00;
+        expected[6] = 0x48;
+        out = 0;
+        if (H5FD__mirror_xmit_encode_uint32((buf+3), v) != 4) {
+            TEST_ERROR;
+        }
+        if (HDmemcmp(buf, expected, 8) != 0) {
+            PRINT_BUFFER_DIFF(buf, expected, 8);
+            TEST_ERROR;
+        }
+        if (H5FD__mirror_xmit_decode_uint32(&out, (buf+3)) != 4) {
+            TEST_ERROR;
+        }
+        if (out != v) {
+            TEST_ERROR;
+        }
+        /* slice */
+        if (H5FD__mirror_xmit_decode_uint32(&out, (buf+4)) != 4) {
+            TEST_ERROR;
+        }
+        if (out != 0x02004800) {
+            TEST_ERROR;
+        }
+
+        /* End of buffer uint32_t
+         */
+        HDbzero(buf, 8);
+        HDbzero(expected, 8);
+        expected[4] = 0x8F;
+        expected[5] = 0x02;
+        expected[6] = 0x00;
+        expected[7] = 0x48;
+        out = 0;
+        if (H5FD__mirror_xmit_encode_uint32((buf+4), v) != 4) {
+            TEST_ERROR;
+        }
+        if (HDmemcmp(buf, expected, 8) != 0) {
+            PRINT_BUFFER_DIFF(buf, expected, 8);
+            TEST_ERROR;
+        }
+        if (H5FD__mirror_xmit_decode_uint32(&out, (buf+4)) != 4) {
+            TEST_ERROR;
+        }
+        if (out != v) {
+            TEST_ERROR;
+        }
+
+    } while (0); /* end uint32_t en/decode */
+
+    /* Test uint64_t encode/decode
+     */
+    do {
+        unsigned char  buf[16];
+        unsigned char  expected[16];
+        const uint64_t v = 0x90DCBE17939CE4BB;
+        uint64_t out = 0;
+
+        /* Start of buffer uint64_t
+         */
+        HDbzero(buf, 16);
+        HDbzero(expected, 16);
+        expected[0] = 0x90;
+        expected[1] = 0xDC;
+        expected[2] = 0xBE;
+        expected[3] = 0x17;
+        expected[4] = 0x93;
+        expected[5] = 0x9C;
+        expected[6] = 0xE4;
+        expected[7] = 0xBB;
+        out = 0;
+        if (H5FD__mirror_xmit_encode_uint64(buf, v) != 8) {
+            TEST_ERROR;
+        }
+        if (HDmemcmp(buf, expected, 16) != 0) {
+            PRINT_BUFFER_DIFF(buf, expected, 16);
+            TEST_ERROR;
+        }
+        if (H5FD__mirror_xmit_decode_uint64(&out, buf) != 8) {
+            TEST_ERROR;
+        }
+        if (out != v) {
+            TEST_ERROR;
+        }
+
+        /* Middle of buffer uint64_t
+         */
+        HDbzero(buf, 16);
+        HDbzero(expected, 16);
+        expected[3]  = 0x90;
+        expected[4]  = 0xDC;
+        expected[5]  = 0xBE;
+        expected[6]  = 0x17;
+        expected[7]  = 0x93;
+        expected[8]  = 0x9C;
+        expected[9]  = 0xE4;
+        expected[10] = 0xBB;
+        out = 0;
+        if (H5FD__mirror_xmit_encode_uint64((buf+3), v) != 8) {
+            TEST_ERROR;
+        }
+        if (HDmemcmp(buf, expected, 16) != 0) {
+            PRINT_BUFFER_DIFF(buf, expected, 16);
+            TEST_ERROR;
+        }
+        if (H5FD__mirror_xmit_decode_uint64(&out, (buf+3)) != 8) {
+            TEST_ERROR;
+        }
+        if (out != v) {
+            TEST_ERROR;
+        }
+        /* slice */
+        if (H5FD__mirror_xmit_decode_uint64(&out, (buf+6)) != 8) {
+            TEST_ERROR;
+        }
+        if (out != 0x17939CE4BB000000) {
+            TEST_ERROR;
+        }
+
+        /* End of buffer uint64_t
+         */
+        HDbzero(buf, 16);
+        HDbzero(expected, 16);
+        expected[8]  = 0x90;
+        expected[9]  = 0xDC;
+        expected[10] = 0xBE;
+        expected[11] = 0x17;
+        expected[12] = 0x93;
+        expected[13] = 0x9C;
+        expected[14] = 0xE4;
+        expected[15] = 0xBB;
+        out = 0;
+        if (H5FD__mirror_xmit_encode_uint64((buf+8), v) != 8) {
+            TEST_ERROR;
+        }
+        if (HDmemcmp(buf, expected, 16) != 0) {
+            PRINT_BUFFER_DIFF(buf, expected, 16);
+            TEST_ERROR;
+        }
+        if (H5FD__mirror_xmit_decode_uint64(&out, (buf+8)) != 8) {
+            TEST_ERROR;
+        }
+        if (out != v) {
+            TEST_ERROR;
+        }
+
+    } while (0); /* end uint64_t en/decode */
+
+    /* Test xmit header structure encode/decode
+     * Write bogus but easily verifiable data to inside a buffer, and compare.
+     * Then decode the buffer and compare the structure contents.
+     * Then repeat from a different offset in the buffer and compare.
+     */
+    do {
+        unsigned char buf[H5FD_MIRROR_XMIT_HEADER_SIZE+8];
+        unsigned char expected[H5FD_MIRROR_XMIT_HEADER_SIZE+8];
+        H5FD_mirror_xmit_t xmit_out;
+        size_t i = 0;
+
+        /* sanity check */
+        if (14 != H5FD_MIRROR_XMIT_HEADER_SIZE) {
+            FAIL_PUTS_ERROR("Header size definition does not match test\n");
+        }
+
+        /* Populate the expected buffer; expect end padding of 0xFF
+         */
+        HDmemset(expected, 0xFF, H5FD_MIRROR_XMIT_HEADER_SIZE+8);
+        for (i=0; i < H5FD_MIRROR_XMIT_HEADER_SIZE; i++) {
+            expected[i+2] = (unsigned char)i;
+        }
+
+        /* Encode, and compare buffer contents
+         * Initial buffer is filled with 0xFF to match expected padding
+         */
+        HDmemset(buf, 0xFF, H5FD_MIRROR_XMIT_HEADER_SIZE+8);
+        if (H5FD_mirror_xmit_encode_header((buf+2), &xmit_mock)
+            != H5FD_MIRROR_XMIT_HEADER_SIZE)
+        {
+            TEST_ERROR;
+        }
+        if (HDmemcmp(buf, expected, H5FD_MIRROR_XMIT_HEADER_SIZE+8) != 0) {
+            PRINT_BUFFER_DIFF(buf, expected, H5FD_MIRROR_XMIT_HEADER_SIZE+8);
+            TEST_ERROR;
+        }
+
+        /* Decode from buffer
+         */
+        if (H5FD_mirror_xmit_decode_header(&xmit_out, (buf+2))
+            != H5FD_MIRROR_XMIT_HEADER_SIZE)
+        {
+            TEST_ERROR;
+        }
+        if (xmit_out.magic         != xmit_mock.magic)         TEST_ERROR;
+        if (xmit_out.version       != xmit_mock.version)       TEST_ERROR;
+        if (xmit_out.session_token != xmit_mock.session_token) TEST_ERROR;
+        if (xmit_out.xmit_count    != xmit_mock.xmit_count)    TEST_ERROR;
+        if (xmit_out.op            != xmit_mock.op)            TEST_ERROR;
+
+        /* Decode from different offset in buffer
+         * Observe changes when ingesting the padding
+         */
+        if (H5FD_mirror_xmit_decode_header(&xmit_out, (buf))
+            != H5FD_MIRROR_XMIT_HEADER_SIZE)
+        {
+            TEST_ERROR;
+        }
+        if (xmit_out.magic         != 0xFFFF0001) TEST_ERROR;
+        if (xmit_out.version       != 0x02)       TEST_ERROR;
+        if (xmit_out.session_token != 0x03040506) TEST_ERROR;
+        if (xmit_out.xmit_count    != 0x0708090A) TEST_ERROR;
+        if (xmit_out.op            != 0x0B)       TEST_ERROR;
+
+    } while (0); /* end xmit header en/decode */
+
+    /* Test xmit set-eoa structure encode/decode
+     * Write bogus but easily verifiable data to inside a buffer, and compare.
+     * Then decode the buffer and compare the structure contents.
+     * Then repeat from a different offset in the buffer and compare.
+     */
+    do {
+        unsigned char buf[H5FD_MIRROR_XMIT_EOA_SIZE+8];
+        unsigned char expected[H5FD_MIRROR_XMIT_EOA_SIZE+8];
+        H5FD_mirror_xmit_eoa_t xmit_in;
+        H5FD_mirror_xmit_eoa_t xmit_out;
+        size_t i = 0;
+
+        /* sanity check */
+        if ((14+9) != H5FD_MIRROR_XMIT_EOA_SIZE) {
+            FAIL_PUTS_ERROR("Header size definition does not match test\n");
+        }
+        if (xmit_mock.op != 0x0D) {
+            FAIL_PUTS_ERROR("shared header structure is not in expected state");
+        }
+
+        /* Populate the expected buffer; expect end padding of 0xFF
+         */
+        HDmemset(expected, 0xFF, H5FD_MIRROR_XMIT_EOA_SIZE+8);
+        for (i=0; i < H5FD_MIRROR_XMIT_EOA_SIZE; i++) {
+            expected[i+2] = (unsigned char)i;
+        }
+
+        /* Set xmit_in
+         */
+        xmit_in.pub = xmit_mock; /* shared/common */
+        xmit_in.type = 0x0E;
+        xmit_in.eoa_addr = 0x0F10111213141516;
+
+        /* Encode, and compare buffer contents
+         * Initial buffer is filled with 0xFF to match expected padding
+         */
+        HDmemset(buf, 0xFF, H5FD_MIRROR_XMIT_EOA_SIZE+8);
+        if (H5FD_mirror_xmit_encode_set_eoa((buf+2), &xmit_in)
+            != H5FD_MIRROR_XMIT_EOA_SIZE)
+        {
+            TEST_ERROR;
+        }
+        if (HDmemcmp(buf, expected, H5FD_MIRROR_XMIT_EOA_SIZE+8) != 0) {
+            PRINT_BUFFER_DIFF(buf, expected, H5FD_MIRROR_XMIT_EOA_SIZE+8);
+            TEST_ERROR;
+        }
+
+        /* Decode from buffer
+         */
+        if (H5FD_mirror_xmit_decode_set_eoa(&xmit_out, (buf+2))
+            != H5FD_MIRROR_XMIT_EOA_SIZE)
+        {
+            TEST_ERROR;
+        }
+        if (xmit_out.pub.magic         != xmit_mock.magic)         TEST_ERROR;
+        if (xmit_out.pub.version       != xmit_mock.version)       TEST_ERROR;
+        if (xmit_out.pub.session_token != xmit_mock.session_token) TEST_ERROR;
+        if (xmit_out.pub.xmit_count    != xmit_mock.xmit_count)    TEST_ERROR;
+        if (xmit_out.pub.op            != xmit_mock.op)            TEST_ERROR;
+        if (xmit_out.type              != 0x0E)                    TEST_ERROR;
+        if (xmit_out.eoa_addr          != 0x0F10111213141516)      TEST_ERROR;
+
+        /* Decode from different offset in buffer
+         * Observe changes when ingesting the padding
+         */
+        if (H5FD_mirror_xmit_decode_set_eoa(&xmit_out, (buf))
+            != H5FD_MIRROR_XMIT_EOA_SIZE)
+        {
+            TEST_ERROR;
+        }
+        if (xmit_out.pub.magic         != 0xFFFF0001)         TEST_ERROR;
+        if (xmit_out.pub.version       != 0x02)               TEST_ERROR;
+        if (xmit_out.pub.session_token != 0x03040506)         TEST_ERROR;
+        if (xmit_out.pub.xmit_count    != 0x0708090A)         TEST_ERROR;
+        if (xmit_out.pub.op            != 0x0B)               TEST_ERROR;
+        if (xmit_out.type              != 0x0C)               TEST_ERROR;
+        if (xmit_out.eoa_addr          != 0x0D0E0F1011121314) TEST_ERROR;
+
+    } while (0); /* end xmit set-eoa en/decode */
+
+    /* Test xmit lock structure encode/decode
+     * Write bogus but easily verifiable data to inside a buffer, and compare.
+     * Then decode the buffer and compare the structure contents.
+     * Then repeat from a different offset in the buffer and compare.
+     */
+    do {
+        unsigned char buf[H5FD_MIRROR_XMIT_LOCK_SIZE+8];
+        unsigned char expected[H5FD_MIRROR_XMIT_LOCK_SIZE+8];
+        H5FD_mirror_xmit_lock_t xmit_in;
+        H5FD_mirror_xmit_lock_t xmit_out;
+        size_t i = 0;
+
+        /* sanity check */
+        if ((14+8) != H5FD_MIRROR_XMIT_LOCK_SIZE) {
+            FAIL_PUTS_ERROR("Header size definition does not match test\n");
+        }
+        if (xmit_mock.op != 0x0D) {
+            FAIL_PUTS_ERROR("shared header structure is not in expected state");
+        }
+
+        /* Populate the expected buffer; expect end padding of 0xFF
+         */
+        HDmemset(expected, 0xFF, H5FD_MIRROR_XMIT_LOCK_SIZE+8);
+        for (i=0; i < H5FD_MIRROR_XMIT_LOCK_SIZE; i++) {
+            expected[i+2] = (unsigned char)i;
+        }
+
+        /* Set xmit_in
+         */
+        xmit_in.pub = xmit_mock; /* shared/common */
+        xmit_in.rw = 0x0E0F101112131415;
+
+        /* Encode, and compare buffer contents
+         * Initial buffer is filled with 0xFF to match expected padding
+         */
+        HDmemset(buf, 0xFF, H5FD_MIRROR_XMIT_LOCK_SIZE+8);
+        if (H5FD_mirror_xmit_encode_lock((buf+2), &xmit_in)
+            != H5FD_MIRROR_XMIT_LOCK_SIZE)
+        {
+            TEST_ERROR;
+        }
+        if (HDmemcmp(buf, expected, H5FD_MIRROR_XMIT_LOCK_SIZE+8) != 0) {
+            PRINT_BUFFER_DIFF(buf, expected, H5FD_MIRROR_XMIT_LOCK_SIZE+8);
+            TEST_ERROR;
+        }
+
+        /* Decode from buffer
+         */
+        if (H5FD_mirror_xmit_decode_lock(&xmit_out, (buf+2))
+            != H5FD_MIRROR_XMIT_LOCK_SIZE)
+        {
+            TEST_ERROR;
+        }
+        if (xmit_out.pub.magic         != xmit_mock.magic)         TEST_ERROR;
+        if (xmit_out.pub.version       != xmit_mock.version)       TEST_ERROR;
+        if (xmit_out.pub.session_token != xmit_mock.session_token) TEST_ERROR;
+        if (xmit_out.pub.xmit_count    != xmit_mock.xmit_count)    TEST_ERROR;
+        if (xmit_out.pub.op            != xmit_mock.op)            TEST_ERROR;
+        if (xmit_out.rw                != 0x0E0F101112131415)      TEST_ERROR;
+
+        /* Decode from different offset in buffer
+         * Observe changes when ingesting the padding
+         */
+        if (H5FD_mirror_xmit_decode_lock(&xmit_out, (buf))
+            != H5FD_MIRROR_XMIT_LOCK_SIZE)
+        {
+            TEST_ERROR;
+        }
+        if (xmit_out.pub.magic         != 0xFFFF0001)         TEST_ERROR;
+        if (xmit_out.pub.version       != 0x02)               TEST_ERROR;
+        if (xmit_out.pub.session_token != 0x03040506)         TEST_ERROR;
+        if (xmit_out.pub.xmit_count    != 0x0708090A)         TEST_ERROR;
+        if (xmit_out.pub.op            != 0x0B)               TEST_ERROR;
+        if (xmit_out.rw                != 0x0C0D0E0F10111213) TEST_ERROR;
+
+    } while (0); /* end xmit lock en/decode */
+
+    /* Test xmit open structure encode/decode
+     * Write bogus but easily verifiable data to inside a buffer, and compare.
+     * Then decode the buffer and compare the structure contents.
+     * Then repeat from a different offset in the buffer and compare.
+     *
+     * Verifies that the first zero character in the filepath will end the
+     * string, with all following bytes in the encoded buffer being zeroed.
+     */
+    do {
+        unsigned char buf[H5FD_MIRROR_XMIT_OPEN_SIZE+8];
+        unsigned char expected[H5FD_MIRROR_XMIT_OPEN_SIZE+8];
+        H5FD_mirror_xmit_open_t xmit_in;
+        H5FD_mirror_xmit_open_t xmit_out;
+        size_t i = 0;
+
+        /* sanity check */
+        if ((14+20+4097) != H5FD_MIRROR_XMIT_OPEN_SIZE) {
+            FAIL_PUTS_ERROR("Header size definition does not match test\n");
+        }
+        if (xmit_mock.op != 0x0D) {
+            FAIL_PUTS_ERROR("shared header structure is not in expected state");
+        }
+
+        /* Populate the expected buffer; expect end padding of 0xFF
+         */
+        HDmemset(expected, 0xFF, H5FD_MIRROR_XMIT_OPEN_SIZE+8);
+        for (i=0; i < H5FD_MIRROR_XMIT_OPEN_SIZE; i++) {
+            /* 0x100 is "zero" in a byte, so encode will treat it as a NULL-
+             * terminator in the filepath string. Expect all zeroes following.
+             */
+            expected[i+2] = (i > 0xFF) ? 0 : (unsigned char)i;
+        }
+
+        /* Set xmit_in
+         */
+        xmit_in.pub = xmit_mock; /* shared/common */
+        xmit_in.flags = 0x0E0F1011;
+        xmit_in.maxaddr = 0x1213141516171819;
+        xmit_in.size_t_blob = 0x1A1B1C1D1E1F2021;
+        for (i=0x22; i < H5FD_MIRROR_XMIT_FILEPATH_MAX+0x22; i++) {
+            /* nonzero values repeat after 0x100, but will not be encoded */
+            xmit_in.filename[i-0x22] = (char)(i % 0x100);
+        }
+        xmit_in.filename[H5FD_MIRROR_XMIT_FILEPATH_MAX-1] = 0;
+
+        /* Encode, and compare buffer contents
+         * Initial buffer is filled with 0xFF to match expected padding
+         */
+        HDmemset(buf, 0xFF, H5FD_MIRROR_XMIT_OPEN_SIZE+8);
+        if (H5FD_mirror_xmit_encode_open((buf+2), &xmit_in)
+            != H5FD_MIRROR_XMIT_OPEN_SIZE)
+        {
+            TEST_ERROR;
+        }
+        if (HDmemcmp(buf, expected, H5FD_MIRROR_XMIT_OPEN_SIZE+8) != 0) {
+            PRINT_BUFFER_DIFF(buf, expected, H5FD_MIRROR_XMIT_OPEN_SIZE+8);
+            TEST_ERROR;
+        }
+
+        /* Decode from buffer
+         */
+        if (H5FD_mirror_xmit_decode_open(&xmit_out, (buf+2))
+            != H5FD_MIRROR_XMIT_OPEN_SIZE)
+        {
+            TEST_ERROR;
+        }
+        if (xmit_out.pub.magic         != xmit_mock.magic)         TEST_ERROR;
+        if (xmit_out.pub.version       != xmit_mock.version)       TEST_ERROR;
+        if (xmit_out.pub.session_token != xmit_mock.session_token) TEST_ERROR;
+        if (xmit_out.pub.xmit_count    != xmit_mock.xmit_count)    TEST_ERROR;
+        if (xmit_out.pub.op            != xmit_mock.op)            TEST_ERROR;
+        if (xmit_out.flags             != xmit_in.flags)           TEST_ERROR;
+        if (xmit_out.maxaddr           != xmit_in.maxaddr)         TEST_ERROR;
+        if (xmit_out.size_t_blob       != xmit_in.size_t_blob)     TEST_ERROR;
+        if (HDstrncmp(xmit_out.filename, xmit_in.filename,
+                      H5FD_MIRROR_XMIT_FILEPATH_MAX)
+            != 0)
+        {
+            PRINT_BUFFER_DIFF(xmit_out.filename, xmit_in.filename,
+                    H5FD_MIRROR_XMIT_FILEPATH_MAX);
+            TEST_ERROR;
+        }
+
+        /* Decode from different offset in buffer
+         * Observe changes when ingesting the padding
+         */
+        if (H5FD_mirror_xmit_decode_open(&xmit_out, (buf))
+            != H5FD_MIRROR_XMIT_OPEN_SIZE)
+        {
+            TEST_ERROR;
+        }
+        if (xmit_out.pub.magic         != 0xFFFF0001)         TEST_ERROR;
+        if (xmit_out.pub.version       != 0x02)               TEST_ERROR;
+        if (xmit_out.pub.session_token != 0x03040506)         TEST_ERROR;
+        if (xmit_out.pub.xmit_count    != 0x0708090A)         TEST_ERROR;
+        if (xmit_out.pub.op            != 0x0B)               TEST_ERROR;
+        if (xmit_out.flags             != 0x0C0D0E0F)         TEST_ERROR;
+        if (xmit_out.maxaddr           != 0x1011121314151617) TEST_ERROR;
+        if (xmit_out.size_t_blob       != 0x18191A1B1C1D1E1F) TEST_ERROR;
+        /* update expected "filepath" in structure */
+        for (i=0x20; i < H5FD_MIRROR_XMIT_FILEPATH_MAX+0x20; i++) {
+            xmit_in.filename[i-0x20] = (i > 0xFF) ? 0 : (char)i;
+        }
+        if (HDstrncmp(xmit_out.filename, xmit_in.filename,
+                      H5FD_MIRROR_XMIT_FILEPATH_MAX)
+            != 0)
+        {
+            PRINT_BUFFER_DIFF(xmit_out.filename, xmit_in.filename,
+                    H5FD_MIRROR_XMIT_FILEPATH_MAX);
+            TEST_ERROR;
+        }
+
+    } while (0); /* end xmit open en/decode */
+
+    /* Test xmit reply structure encode/decode
+     * Write bogus but easily verifiable data to inside a buffer, and compare.
+     * Then decode the buffer and compare the structure contents.
+     * Then repeat from a different offset in the buffer and compare.
+     *
+     * Verifies that the first zero character in the filepath will end the
+     * string, with all following bytes in the encoded buffer being zeroed.
+     */
+    do {
+        unsigned char buf[H5FD_MIRROR_XMIT_REPLY_SIZE+8];
+        unsigned char expected[H5FD_MIRROR_XMIT_REPLY_SIZE+8];
+        H5FD_mirror_xmit_reply_t xmit_in;
+        H5FD_mirror_xmit_reply_t xmit_out;
+        size_t i = 0;
+
+        /* sanity check */
+        if ((14+4+256) != H5FD_MIRROR_XMIT_REPLY_SIZE) {
+            FAIL_PUTS_ERROR("Header size definition does not match test\n");
+        }
+        if (xmit_mock.op != 0x0D) {
+            FAIL_PUTS_ERROR("shared header structure is not in expected state");
+        }
+
+        /* Populate the expected buffer; expect end padding of 0xFF
+         */
+        HDmemset(expected, 0xFF, H5FD_MIRROR_XMIT_REPLY_SIZE+8);
+        for (i=0; i < H5FD_MIRROR_XMIT_REPLY_SIZE; i++) {
+            /* 0x100 is "zero" in a byte, so encode will treat it as a NULL-
+             * terminator in the filepath string. Expect all zeroes following.
+             */
+            expected[i+2] = (i > 0xFF) ? 0 : (unsigned char)i;
+        }
+
+        /* Set xmit_in
+         */
+        xmit_in.pub = xmit_mock; /* shared/common */
+        xmit_in.status = 0x0E0F1011;
+        for (i=0x12; i < H5FD_MIRROR_STATUS_MESSAGE_MAX+0x12; i++) {
+            /* nonzero values repeat after 0x100, but will not be encoded */
+            xmit_in.message[i-0x12] = (char)(i % 0x100);
+        }
+        xmit_in.message[H5FD_MIRROR_STATUS_MESSAGE_MAX-1] = 0;
+
+        /* Encode, and compare buffer contents
+         * Initial buffer is filled with 0xFF to match expected padding
+         */
+        HDmemset(buf, 0xFF, H5FD_MIRROR_XMIT_REPLY_SIZE+8);
+        if (H5FD_mirror_xmit_encode_reply((buf+2), &xmit_in)
+            != H5FD_MIRROR_XMIT_REPLY_SIZE)
+        {
+            TEST_ERROR;
+        }
+        if (HDmemcmp(buf, expected, H5FD_MIRROR_XMIT_REPLY_SIZE+8) != 0) {
+            PRINT_BUFFER_DIFF(buf, expected, H5FD_MIRROR_XMIT_REPLY_SIZE+8);
+            TEST_ERROR;
+        }
+
+        /* Decode from buffer
+         */
+        if (H5FD_mirror_xmit_decode_reply(&xmit_out, (buf+2))
+            != H5FD_MIRROR_XMIT_REPLY_SIZE)
+        {
+            TEST_ERROR;
+        }
+        if (xmit_out.pub.magic         != xmit_mock.magic)         TEST_ERROR;
+        if (xmit_out.pub.version       != xmit_mock.version)       TEST_ERROR;
+        if (xmit_out.pub.session_token != xmit_mock.session_token) TEST_ERROR;
+        if (xmit_out.pub.xmit_count    != xmit_mock.xmit_count)    TEST_ERROR;
+        if (xmit_out.pub.op            != xmit_mock.op)            TEST_ERROR;
+        if (xmit_out.status            != xmit_in.status)          TEST_ERROR;
+        if (HDstrncmp(xmit_out.message, xmit_in.message,
+                      H5FD_MIRROR_STATUS_MESSAGE_MAX)
+            != 0)
+        {
+            PRINT_BUFFER_DIFF(xmit_out.message, xmit_in.message,
+                    H5FD_MIRROR_STATUS_MESSAGE_MAX);
+            TEST_ERROR;
+        }
+
+        /* Decode from different offset in buffer
+         * Observe changes when ingesting the padding
+         */
+        if (H5FD_mirror_xmit_decode_reply(&xmit_out, (buf))
+            != H5FD_MIRROR_XMIT_REPLY_SIZE)
+        {
+            TEST_ERROR;
+        }
+        if (xmit_out.pub.magic         != 0xFFFF0001)         TEST_ERROR;
+        if (xmit_out.pub.version       != 0x02)               TEST_ERROR;
+        if (xmit_out.pub.session_token != 0x03040506)         TEST_ERROR;
+        if (xmit_out.pub.xmit_count    != 0x0708090A)         TEST_ERROR;
+        if (xmit_out.pub.op            != 0x0B)               TEST_ERROR;
+        if (xmit_out.status            != 0x0C0D0E0F)         TEST_ERROR;
+        /* update expected "message" in structure */
+        for (i=0x10; i < H5FD_MIRROR_STATUS_MESSAGE_MAX+0x10; i++) {
+            xmit_in.message[i-0x10] = (i > 0xFF) ? 0 : (char)i;
+        }
+        if (HDstrncmp(xmit_out.message, xmit_in.message,
+                      H5FD_MIRROR_STATUS_MESSAGE_MAX)
+            != 0)
+        {
+            PRINT_BUFFER_DIFF(xmit_out.message, xmit_in.message,
+                    H5FD_MIRROR_STATUS_MESSAGE_MAX);
+            TEST_ERROR;
+        }
+
+    } while (0); /* end xmit reply en/decode */
+
+    /* Test xmit write structure encode/decode
+     * Write bogus but easily verifiable data to inside a buffer, and compare.
+     * Then decode the buffer and compare the structure contents.
+     * Then repeat from a different offset in the buffer and compare.
+     */
+    do {
+        unsigned char buf[H5FD_MIRROR_XMIT_WRITE_SIZE+8];
+        unsigned char expected[H5FD_MIRROR_XMIT_WRITE_SIZE+8];
+        H5FD_mirror_xmit_write_t xmit_in;
+        H5FD_mirror_xmit_write_t xmit_out;
+        size_t i = 0;
+
+        /* sanity check */
+        if ((14+17) != H5FD_MIRROR_XMIT_WRITE_SIZE) {
+            FAIL_PUTS_ERROR("Header size definition does not match test\n");
+        }
+        if (xmit_mock.op != 0x0D) {
+            FAIL_PUTS_ERROR("shared header structure is not in expected state");
+        }
+
+        /* Populate the expected buffer; expect end padding of 0xFF
+         */
+        HDmemset(expected, 0xFF, H5FD_MIRROR_XMIT_WRITE_SIZE+8);
+        for (i=0; i < H5FD_MIRROR_XMIT_WRITE_SIZE; i++) {
+            expected[i+2] = (unsigned char)i;
+        }
+
+        /* Set xmit_in
+         */
+        xmit_in.pub    = xmit_mock; /* shared/common */
+        xmit_in.type   = 0x0E;
+        xmit_in.offset = 0x0F10111213141516;
+        xmit_in.size   = 0x1718191A1B1C1D1E;
+
+        /* Encode, and compare buffer contents
+         * Initial buffer is filled with 0xFF to match expected padding
+         */
+        HDmemset(buf, 0xFF, H5FD_MIRROR_XMIT_WRITE_SIZE+8);
+        if (H5FD_mirror_xmit_encode_write((buf+2), &xmit_in)
+            != H5FD_MIRROR_XMIT_WRITE_SIZE)
+        {
+            TEST_ERROR;
+        }
+        if (HDmemcmp(buf, expected, H5FD_MIRROR_XMIT_WRITE_SIZE+8) != 0) {
+            PRINT_BUFFER_DIFF(buf, expected, H5FD_MIRROR_XMIT_WRITE_SIZE+8);
+            TEST_ERROR;
+        }
+
+        /* Decode from buffer
+         */
+        if (H5FD_mirror_xmit_decode_write(&xmit_out, (buf+2))
+            != H5FD_MIRROR_XMIT_WRITE_SIZE)
+        {
+            TEST_ERROR;
+        }
+        if (xmit_out.pub.magic         != xmit_mock.magic)         TEST_ERROR;
+        if (xmit_out.pub.version       != xmit_mock.version)       TEST_ERROR;
+        if (xmit_out.pub.session_token != xmit_mock.session_token) TEST_ERROR;
+        if (xmit_out.pub.xmit_count    != xmit_mock.xmit_count)    TEST_ERROR;
+        if (xmit_out.pub.op            != xmit_mock.op)            TEST_ERROR;
+        if (xmit_out.type              != 0x0E)                    TEST_ERROR;
+        if (xmit_out.offset            != 0x0F10111213141516)      TEST_ERROR;
+        if (xmit_out.size              != 0x1718191A1B1C1D1E)      TEST_ERROR;
+
+        /* Decode from different offset in buffer
+         * Observe changes when ingesting the padding
+         */
+        if (H5FD_mirror_xmit_decode_write(&xmit_out, (buf))
+            != H5FD_MIRROR_XMIT_WRITE_SIZE)
+        {
+            TEST_ERROR;
+        }
+        if (xmit_out.pub.magic         != 0xFFFF0001)         TEST_ERROR;
+        if (xmit_out.pub.version       != 0x02)               TEST_ERROR;
+        if (xmit_out.pub.session_token != 0x03040506)         TEST_ERROR;
+        if (xmit_out.pub.xmit_count    != 0x0708090A)         TEST_ERROR;
+        if (xmit_out.pub.op            != 0x0B)               TEST_ERROR;
+        if (xmit_out.type              != 0x0C)               TEST_ERROR;
+        if (xmit_out.offset            != 0x0D0E0F1011121314) TEST_ERROR;
+        if (xmit_out.size              != 0x15161718191A1B1C) TEST_ERROR;
+
+    } while (0); /* end xmit write en/decode */
+
+    PASSED();
+    return 0;
+
+error:
+    return -1;
+} /* end test_xmit_encode_decode */
+
+
+/* ---------------------------------------------------------------------------
+ * Function:    create_mirroring_split_fapl
+ *
+ * Purpose:     Create and populate a mirroring FAPL ID.
+ *              Creates target files with the given base name -- ideally the
+ *              test name -- and creates mirroring/split FAPL set to use the
+ *              global mirroring info and a sec2 R/W channel driver.
+ *
+ *              TODO: receive target IP from caller?
+ *
+ * Return:      Success: HID of the top-level (splitter) FAPL, a non-negative
+ *                       value.
+ *              Failure: H5I_INVALID_HID, a negative value.
+ *
+ * Programmer:  Jacob Smith
+ *              2019
+ * ---------------------------------------------------------------------------
+ */
+static hid_t
+create_mirroring_split_fapl(const char                      *_basename,
+                            struct mirrortest_filenames     *names)
+{
+    H5FD_splitter_vfd_config_t  splitter_config;
+    H5FD_mirror_fapl_t          mirror_conf;
+    hid_t                       ret_value = H5I_INVALID_HID;
+
+    if (_basename == NULL || *_basename == '\0') {
+        TEST_ERROR;
+    }
+
+    splitter_config.magic = H5FD_SPLITTER_MAGIC;
+    splitter_config.version = H5FD_CURR_SPLITTER_VFD_CONFIG_VERSION;
+    splitter_config.ignore_wo_errs = FALSE;
+
+    /* Create Splitter R/W channel driver (sec2)
+     */
+    splitter_config.rw_fapl_id = H5Pcreate(H5P_FILE_ACCESS);
+    if (H5I_INVALID_HID == splitter_config.rw_fapl_id) {
+        TEST_ERROR;
+    }
+    if (H5Pset_fapl_sec2(splitter_config.rw_fapl_id) == FAIL) {
+        TEST_ERROR;
+    }
+
+    /* Create Splitter W/O channel driver (mirror)
+     */
+    mirror_conf.magic = H5FD_MIRROR_FAPL_MAGIC;
+    mirror_conf.version = H5FD_MIRROR_CURR_FAPL_T_VERSION;
+    mirror_conf.handshake_port = SERVER_HANDSHAKE_PORT;
+    if (HDstrncpy(mirror_conf.remote_ip, SERVER_IP_ADDRESS,
+            H5FD_MIRROR_MAX_IP_LEN)
+        == NULL)
+    {
+        TEST_ERROR;
+    }
+    splitter_config.wo_fapl_id = H5Pcreate(H5P_FILE_ACCESS);
+    if (H5I_INVALID_HID == splitter_config.wo_fapl_id) {
+        TEST_ERROR;
+    }
+    if (H5Pset_fapl_mirror(splitter_config.wo_fapl_id, &mirror_conf) == FAIL) {
+        TEST_ERROR;
+    }
+
+    /* Build r/w, w/o, and log file paths
+     */
+    if (build_paths(_basename, &splitter_config, names) < 0) {
+        TEST_ERROR;
+    }
+
+    /* Set file paths for w/o and logfile
+     */
+    if (HDstrncpy(splitter_config.wo_path, (const char *)names->wo,
+            H5FD_SPLITTER_PATH_MAX)
+        == NULL)
+    {
+        TEST_ERROR;
+    }
+    if (HDstrncpy(splitter_config.log_file_path, (const char *)names->log,
+            H5FD_SPLITTER_PATH_MAX)
+        == NULL)
+    {
+        TEST_ERROR;
+    }
+
+    /* Create Splitter FAPL
+     */
+    ret_value = H5Pcreate(H5P_FILE_ACCESS);
+    if (H5I_INVALID_HID == ret_value) {
+        TEST_ERROR;
+    }
+    if (H5Pset_fapl_splitter(ret_value, &splitter_config) == FAIL) {
+        TEST_ERROR;
+    }
+
+    /* Close FAPLs created for child channels
+     */
+    if (H5Pclose(splitter_config.rw_fapl_id) < 0) {
+        TEST_ERROR;
+    }
+    splitter_config.rw_fapl_id = H5I_INVALID_HID;
+    if (H5Pclose(splitter_config.wo_fapl_id) < 0) {
+        TEST_ERROR;
+    }
+    splitter_config.wo_fapl_id = H5I_INVALID_HID;
+
+    return ret_value;
+
+error:
+    if (splitter_config.wo_fapl_id >= 0) {
+        (void)H5Pclose(splitter_config.wo_fapl_id);
+    }
+    if (splitter_config.rw_fapl_id >= 0) {
+        (void)H5Pclose(splitter_config.rw_fapl_id);
+    }
+    if (ret_value >= 0) {
+        (void)H5Pclose(ret_value);
+    }
+    return H5I_INVALID_HID;
+} /* end create_mirroring_split_fapl() */
+
+
+/* ---------------------------------------------------------------------------
+ * Function:    test_create_and_close
+ *
+ * Purpose:     Test/demonstrate a do-nothing file open and close.
+ *
+ *              Verifying file existence and contents is part of other tests.
+ *
+ *              TODO: receive target IP from caller?
+ *
+ * Return:      Success: 0
+ *              Failure: -1
+ *
+ * Programmer:  Jacob Smith
+ *              2019-12-17
+ * ---------------------------------------------------------------------------
+ */
+static int
+test_create_and_close(void)
+{
+    struct mirrortest_filenames names;
+    hid_t file_id = H5I_INVALID_HID;
+    hid_t fapl_id = H5P_DEFAULT;
+
+    TESTING("File creation and immediate close");
+
+    /* Create FAPL for Splitter[sec2|mirror]
+     */
+    fapl_id = create_mirroring_split_fapl("basic_create", &names);
+    if (H5I_INVALID_HID == fapl_id) {
+        TEST_ERROR;
+    }
+
+    /* -------------------- */
+    /* TEST: Create and Close */
+
+    file_id = H5Fcreate(names.rw, H5F_ACC_TRUNC, H5P_DEFAULT, fapl_id);
+    if (H5I_INVALID_HID == file_id) {
+        TEST_ERROR;
+    }
+
+    /* -------------------- */
+    /* Standard cleanup */
+
+    if (H5Fclose(file_id) == FAIL) {
+        TEST_ERROR;
+    }
+    if (fapl_id != H5P_DEFAULT && fapl_id >= 0) {
+        if (H5Pclose(fapl_id) == FAIL) {
+            TEST_ERROR;
+        }
+    }
+
+    PASSED();
+    return 0;
+
+error:
+    H5E_BEGIN_TRY{
+        (void)H5Fclose(file_id);
+        (void)H5Pclose(fapl_id);
+    } H5E_END_TRY;
+    return -1;
+} /* end test_create_and_close() */
+
+
+/* ----------------------------------------------------------------------------
+ * Function:    create_datasets
+ *
+ * Purpose:     Given a file ID and least and greateset dataset indices, create
+ *              populated chunked datasets in the target file from min_dset to
+ *              (and including) max_dset.
+ *              Uses #defined constants to determine chunk and dataset sizes
+ *              and values.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ * Programmer:  Jacob Smith
+ *              2019-08-14
+ * ----------------------------------------------------------------------------
+ */
+static herr_t
+create_datasets(hid_t    file_id,
+                unsigned min_dset,
+                unsigned max_dset)
+{
+    hid_t       dataspace_ids[MAX_DSET_COUNT + 1];
+    hid_t       dataset_ids[MAX_DSET_COUNT + 1];
+    hid_t       filespace_ids[MAX_DSET_COUNT + 1];
+    int         data_chunk[CHUNK_DIM][CHUNK_DIM];
+    unsigned int        i, j, k, l, m;
+    hsize_t     offset[2];
+    hid_t       memspace_id   = H5I_INVALID_HID;
+    hsize_t     a_size[2]     = {CHUNK_DIM, CHUNK_DIM};
+    hsize_t     chunk_dims[2] = {CHUNK_DIM, CHUNK_DIM};
+    hsize_t     dset_dims[2]  = {DSET_DIM, DSET_DIM};
+
+    HDassert(file_id >= 0);
+    HDassert(min_dset <= max_dset);
+    HDassert(max_dset <= MAX_DSET_COUNT);
+
+    LOGPRINT(2, "create_dataset()\n");
+
+    /* ---------------------------------
+     * "Clear" ID arrays
+     */
+
+    for (i = 0; i < MAX_DSET_COUNT; i++) {
+        LOGPRINT(3, "clearing IDs [%d]\n", i);
+        dataspace_ids[i] = H5I_INVALID_HID;
+        dataset_ids[i] = H5I_INVALID_HID;
+        filespace_ids[i] = H5I_INVALID_HID;
+    }
+
+    /* ---------------------------------
+     * Generate dataspace, dataset, and 'filespace' IDs
+     */
+
+    if (_create_chunking_ids(file_id, min_dset, max_dset, chunk_dims,
+            dset_dims, dataspace_ids, filespace_ids, dataset_ids, &memspace_id)
+        == FAIL)
+    {
+        TEST_ERROR;
+    }
+
+    /* ---------------------------------
+     * Initialize (write) all datasets in a "round robin"...
+     * for a given chunk 'location', write chunk data to each dataset.
+     */
+
+    for (i = 0; i < DSET_DIM; i += CHUNK_DIM)
+    {
+        LOGPRINT(3, "i: %d\n", i);
+        for (j = 0; j < DSET_DIM; j += CHUNK_DIM)
+        {
+            LOGPRINT(3, "  j: %d\n", j);
+            for (m = min_dset; m <= max_dset; m++)
+            {
+                LOGPRINT(3, "    m: %d\n", m);
+                for (k = 0; k < CHUNK_DIM; k++)
+                {
+                    for (l = 0; l < CHUNK_DIM; l++)
+                    {
+                        data_chunk[k][l] = (int)((DSET_DIM * DSET_DIM * m) +
+                                                 (DSET_DIM * (i + k)) + j + l);
+                        LOGPRINT(3, "      data_chunk[%d][%d]: %d\n",
+                                 k, l, data_chunk[k][l]);
+                    }
+                }
+
+                /* select on disk hyperslab */
+                offset[0] = (hsize_t)i;
+                offset[1] = (hsize_t)j;
+                LOGPRINT(3, "    H5Sselect_hyperslab()\n");
+                if (H5Sselect_hyperslab(filespace_ids[m], H5S_SELECT_SET,
+                        offset, NULL, a_size, NULL)
+                    < 0)
+                {
+                    TEST_ERROR;
+                }
+
+                LOGPRINT(3, "    H5Dwrite()\n");
+                if (H5Dwrite(dataset_ids[m], H5T_NATIVE_INT, memspace_id,
+                        filespace_ids[m], H5P_DEFAULT, data_chunk)
+                    < 0)
+                {
+                    TEST_ERROR;
+                }
+
+            }
+        }
+    }
+
+    /* ---------------------------------
+     * Read and verify data from datasets
+     */
+
+    if (_verify_datasets(min_dset, max_dset, filespace_ids, dataset_ids,
+                memspace_id)
+        == FAIL)
+    {
+        TEST_ERROR;
+    }
+
+    /* ---------------------------------
+     * Cleanup
+     */
+
+    if (_close_chunking_ids(min_dset, max_dset, dataspace_ids, filespace_ids,
+                dataset_ids, &memspace_id)
+        == FAIL)
+    {
+        TEST_ERROR;
+    }
+
+    return SUCCEED;
+
+error:
+    (void)_close_chunking_ids(min_dset, max_dset, dataspace_ids,
+                filespace_ids, dataset_ids, &memspace_id);
+    LOGPRINT(1, "create_datasets() FAILED\n");
+    return FAIL;
+} /* end create_datasets() */
+
+
+/* ----------------------------------------------------------------------------
+ * Function:   _create_chunking_ids
+ *
+ * Purpose:    Create new IDs to be used with the associated file.
+ *
+ * Return:     SUCCEED/FAIL
+ *
+ * Programer:  Jacob Smith
+ *             2019
+ * ----------------------------------------------------------------------------
+ */
+static herr_t
+_create_chunking_ids(hid_t     file_id,
+                     unsigned  min_dset,
+                     unsigned  max_dset,
+                     hsize_t  *chunk_dims,
+                     hsize_t  *dset_dims,
+                     hid_t    *dataspace_ids,
+                     hid_t    *filespace_ids,
+                     hid_t    *dataset_ids,
+                     hid_t    *memspace_id)
+{
+    char     dset_name[DSET_NAME_LEN + 1];
+    unsigned m         = 0;
+    hid_t    dcpl_id   = H5I_INVALID_HID;
+
+    LOGPRINT(2, "_create_chunking_ids()\n");
+
+    /* --------------------
+     * Create chunking DCPL
+     */
+
+    dcpl_id = H5Pcreate(H5P_DATASET_CREATE);
+    if (dcpl_id < 0) {
+        TEST_ERROR;
+    }
+    if (H5Pset_chunk(dcpl_id, 2, chunk_dims) == FAIL) {
+        TEST_ERROR;
+    }
+
+    /* --------------------
+     * Create dataspace IDs
+     */
+
+    for (m = min_dset; m <= max_dset; m++) {
+        dataspace_ids[m] = H5Screate_simple(2, dset_dims, NULL);
+        if (dataspace_ids[m] < 0) {
+            HDsnprintf(mesg, MIRR_MESG_SIZE,
+                    "unable to create dataspace ID %d\n", m);
+            FAIL_PUTS_ERROR(mesg);
+        }
+    }
+
+    /* --------------------
+     * Create dataset IDs
+     */
+
+    for (m = min_dset; m <= max_dset; m++) {
+        if (HDsnprintf(dset_name, DSET_NAME_LEN, "/dset%03d", m)
+            > DSET_NAME_LEN)
+        {
+            HDsnprintf(mesg, MIRR_MESG_SIZE,
+                    "unable to compose dset name %d\n", m);
+            FAIL_PUTS_ERROR(mesg);
+        }
+
+        dataset_ids[m] = H5Dcreate(file_id, dset_name, H5T_STD_I32BE,
+                dataspace_ids[m], H5P_DEFAULT, dcpl_id, H5P_DEFAULT);
+        if (dataset_ids[m] < 0) {
+            HDsnprintf(mesg, MIRR_MESG_SIZE,
+                    "unable to create dset ID %d\n", m);
+            FAIL_PUTS_ERROR(mesg);
+        }
+    }
+
+    /* --------------------
+     * Get file space IDs
+     */
+
+    for (m = min_dset; m <= max_dset; m++) {
+        filespace_ids[m] = H5Dget_space(dataset_ids[m]);
+        if (filespace_ids[m] < 0) {
+            HDsnprintf(mesg, MIRR_MESG_SIZE,
+                    "unable to create filespace ID %d\n", m);
+            FAIL_PUTS_ERROR(mesg);
+        }
+    }
+
+    /* --------------------
+     * Create mem space to be used to read and write chunks
+     */
+
+    *memspace_id = H5Screate_simple(2, chunk_dims, NULL);
+    if (*memspace_id < 0) {
+        TEST_ERROR;
+    }
+
+    /* --------------------
+     * Clean up the DCPL, even if there were errors before
+     */
+
+    if (dcpl_id != H5P_DEFAULT && dcpl_id != H5I_INVALID_HID) {
+        if (H5Pclose(dcpl_id) == FAIL) {
+            TEST_ERROR;
+        }
+    }
+
+    return SUCCEED;
+
+error:
+    if (dcpl_id != H5P_DEFAULT && dcpl_id != H5I_INVALID_HID) {
+        (void)H5Pclose(dcpl_id);
+    }
+    LOGPRINT(1, "_create_chunking_ids() FAILED\n");
+    return FAIL;
+} /* end _create_chunking_ids() */
+
+
+/* ----------------------------------------------------------------------------
+ * Function:    _open_chunking_ids
+ *
+ * Purpose:     Open/access IDs from the given file.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ * Programmer:  Jacob Smith
+ *              2019
+ * ----------------------------------------------------------------------------
+ */
+static herr_t
+_open_chunking_ids(
+        hid_t     file_id,
+        unsigned  min_dset,
+        unsigned  max_dset,
+        hsize_t  *chunk_dims,
+        hid_t    *filespace_ids,
+        hid_t    *dataset_ids,
+        hid_t    *memspace_id)
+{
+    char     dset_name[DSET_NAME_LEN+1];
+    unsigned m = 0;
+
+    LOGPRINT(2, "_open_chunking_ids()\n");
+
+    /* --------------------
+     * Open dataset IDs
+     */
+
+    for (m = min_dset; m <= max_dset; m++) {
+        if (HDsnprintf(dset_name, DSET_NAME_LEN, "/dset%03d", m)
+            > DSET_NAME_LEN)
+        {
+            HDsnprintf(mesg, MIRR_MESG_SIZE,
+                    "unable to compose dset name %d\n", m);
+            FAIL_PUTS_ERROR(mesg);
+        }
+
+        dataset_ids[m] = H5Dopen2(file_id, dset_name, H5P_DEFAULT);
+        if (dataset_ids[m] < 0) {
+            HDsnprintf(mesg, MIRR_MESG_SIZE, "unable to open dset ID %d\n", m);
+            FAIL_PUTS_ERROR(mesg);
+        }
+    }
+
+    /* --------------------
+     * Open filespace IDs
+     */
+
+    for (m = min_dset; m <= max_dset; m++) {
+        filespace_ids[m] = H5Dget_space(dataset_ids[m]);
+        if (filespace_ids[m] < 0) {
+            HDsnprintf(mesg, MIRR_MESG_SIZE,
+                    "unable to get filespace ID %d\n", m);
+            FAIL_PUTS_ERROR(mesg);
+        }
+    }
+
+    /* --------------------
+     * Create mem space to be used to read and write chunks
+     */
+
+    *memspace_id = H5Screate_simple(2, chunk_dims, NULL);
+    if (*memspace_id < 0) {
+        TEST_ERROR;
+    }
+
+    return SUCCEED;
+
+error:
+    LOGPRINT(1, "_open_chunking_ids() FAILED\n");
+    return FAIL;
+} /* end _open_chunking_ids() */
+
+
+/* ---------------------------------------------------------------------------
+ * Function:    _close_chunking_ids
+ *
+ * Purpose:     Close IDs that were created or opened.
+ *              Pass NULL into `dataspace_ids` when closing items opened with
+ *              _open_chunking_ids(). (as opposed to created IDs)
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ * Programmer:  Jacob Smith
+ *              2019
+ * ---------------------------------------------------------------------------
+ */
+static herr_t
+_close_chunking_ids(unsigned min_dset,
+                    unsigned max_dset,
+                    hid_t *dataspace_ids,
+                    hid_t *filespace_ids,
+                    hid_t *dataset_ids,
+                    hid_t *memspace_id)
+{
+    unsigned m;
+
+    LOGPRINT(2, "_close_chunking_ids()\n");
+
+    for (m = min_dset; m <= max_dset; m++) {
+        LOGPRINT(3, "closing ids[%d]\n", m);
+        if (dataspace_ids) {
+            if (H5Sclose(dataspace_ids[m]) < 0) {
+                HDsnprintf(mesg, MIRR_MESG_SIZE,
+                        "unable to close dataspace_id[%d]\n", m);
+                FAIL_PUTS_ERROR(mesg);
+            }
+        }
+        if (H5Dclose(dataset_ids[m]) < 0) {
+            HDsnprintf(mesg, MIRR_MESG_SIZE,
+                        "unable to close dataset_id[%d]\n", m);
+            FAIL_PUTS_ERROR(mesg);
+        }
+        if (H5Sclose(filespace_ids[m]) < 0) {
+            HDsnprintf(mesg, MIRR_MESG_SIZE,
+                        "unable to close filespace_id[%d]\n", m);
+            FAIL_PUTS_ERROR(mesg);
+        }
+    }
+
+    if ( (*memspace_id != H5I_INVALID_HID) &&
+         (H5Sclose(*memspace_id) < 0) )
+    {
+        TEST_ERROR;
+    }
+
+    return SUCCEED;
+
+error:
+    LOGPRINT(1, "_close_chunking_ids() FAILED\n");
+    return FAIL;
+} /* end _close_chunking_ids() */
+
+
+/* ---------------------------------------------------------------------------
+ * Function:    _verify_datasets
+ *
+ * Purpose:     Check that each chunk's contents are as expected, as pertaining
+ *              to create_datasets().
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ * Programmer:  Jacob Smith
+ *              2019
+ * ---------------------------------------------------------------------------
+ */
+static herr_t
+_verify_datasets(unsigned  min_dset,
+                 unsigned  max_dset,
+                 hid_t    *filespace_ids,
+                 hid_t    *dataset_ids,
+                 hid_t     memspace_id)
+{
+    unsigned i, j, k, l, m;
+    int      data_chunk[CHUNK_DIM][CHUNK_DIM];
+    hsize_t  offset[2];
+    hsize_t  a_size[2] = {CHUNK_DIM, CHUNK_DIM};
+
+    LOGPRINT(2, "_verify_datasets()\n");
+
+    for (i = 0; i < DSET_DIM; i += CHUNK_DIM)
+    {
+        LOGPRINT(3, "i: %d\n", i);
+        for (j = 0; j < DSET_DIM; j += CHUNK_DIM)
+        {
+            LOGPRINT(3, "  j: %d\n", j);
+            for (m = min_dset; m <= max_dset; m++)
+            {
+                LOGPRINT(3, "    m: %d\n", m);
+
+                /* select on disk hyperslab */
+                offset[0] = (hsize_t)i;
+                offset[1] = (hsize_t)j;
+                if (H5Sselect_hyperslab(filespace_ids[m], H5S_SELECT_SET,
+                        offset, NULL, a_size, NULL)
+                    < 0)
+                {
+                    TEST_ERROR;
+                }
+
+                if (H5Dread(dataset_ids[m], H5T_NATIVE_INT, memspace_id,
+                        filespace_ids[m], H5P_DEFAULT, data_chunk)
+                    < 0)
+                {
+                    HDsnprintf(mesg, MIRR_MESG_SIZE,
+                               "      H5Dread() [%d][%d][%d]\n",
+                               i, j, m);
+                    FAIL_PUTS_ERROR(mesg);
+                }
+
+                for (k = 0; k < CHUNK_DIM; k++) {
+                    for (l = 0; l < CHUNK_DIM; l++) {
+                        if ((unsigned)data_chunk[k][l]
+                            !=
+                            ((DSET_DIM * DSET_DIM * m) +
+                             (DSET_DIM * (i + k)) + j + l))
+                        {
+                            HDsnprintf(mesg, MIRR_MESG_SIZE,
+                                    "      MISMATCH [%d][%d][%d][%d][%d]\n",
+                                    i, j, m, k, l);
+                            FAIL_PUTS_ERROR(mesg);
+                        }
+                    }
+                }
+
+            }
+        }
+    }
+
+    return SUCCEED;
+
+error:
+    LOGPRINT(1, "_verify_datasets() FAILED\n");
+    return FAIL;
+} /* end _verify_datasets() */
+
+
+/* ---------------------------------------------------------------------------
+ * Function:    verify_datasets
+ *
+ * Purpose:     Inspect the datasets in the file created by create_datasets().
+ *              Wrapper for _verify_datasets() -- this function sets up and
+ *              tears down accessor information.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ * Programmer:  Jacob Smith
+ *              2019
+ * ---------------------------------------------------------------------------
+ */
+static herr_t
+verify_datasets(hid_t    file_id,
+                unsigned min_dset,
+                unsigned max_dset)
+{
+    hid_t    dataset_ids[MAX_DSET_COUNT + 1];
+    hid_t    filespace_ids[MAX_DSET_COUNT + 1];
+    unsigned i;
+    hid_t    memspace_id   = H5I_INVALID_HID;
+    hsize_t  chunk_dims[2] = {CHUNK_DIM, CHUNK_DIM};
+
+    HDassert(file_id >= 0);
+    HDassert(min_dset <= max_dset);
+    HDassert(max_dset <= MAX_DSET_COUNT);
+
+    LOGPRINT(2, "verify_datasets()\n");
+
+    /* ---------------------------------
+     * "Clear" ID arrays
+     */
+
+    for (i = 0; i < MAX_DSET_COUNT; i++) {
+        LOGPRINT(3, "clearing IDs [%d]\n", i);
+        dataset_ids[i] = H5I_INVALID_HID;
+        filespace_ids[i] = H5I_INVALID_HID;
+    }
+
+    /* ---------------------------------
+     * Generate dataspace, dataset, and 'filespace' IDs
+     */
+
+    if (_open_chunking_ids(file_id, min_dset, max_dset, chunk_dims,
+            filespace_ids, dataset_ids, &memspace_id)
+        == FAIL)
+    {
+        TEST_ERROR;
+    }
+
+    /* ---------------------------------
+     * Read and verify data from datasets
+     */
+
+    if (_verify_datasets(min_dset, max_dset, filespace_ids, dataset_ids,
+            memspace_id)
+        == FAIL)
+    {
+        TEST_ERROR;
+    }
+
+    /* ---------------------------------
+     * Cleanup
+     */
+
+    if (_close_chunking_ids(min_dset, max_dset, NULL, filespace_ids,
+                dataset_ids, &memspace_id)
+        == FAIL)
+    {
+        TEST_ERROR;
+    }
+
+    return SUCCEED;
+
+error:
+    LOGPRINT(1, "verify_datasets() FAILED\n");
+    (void)_close_chunking_ids(min_dset, max_dset, NULL, filespace_ids,
+            dataset_ids, &memspace_id);
+    return FAIL;
+
+} /* end verify_datasets() */
+
+
+/* ---------------------------------------------------------------------------
+ * Function:    test_basic_dataset_write
+ *
+ * Purpose:     Create and close files; repoen files and write a dataset,
+ *              close; compare files.
+ *
+ *              TODO: receive target IP from caller?
+ *
+ * Return:      Success: 0
+ *              Failure: -1
+ *
+ * Programmer:  Jacob Smith
+ *              2019
+ * ---------------------------------------------------------------------------
+ */
+static int
+test_basic_dataset_write(void)
+{
+    struct mirrortest_filenames names;
+    hid_t       file_id = H5I_INVALID_HID;
+    hid_t       fapl_id = H5P_DEFAULT;
+    hid_t       dset_id = H5I_INVALID_HID;
+    hid_t       dspace_id = H5I_INVALID_HID;
+    hid_t       dtype_id = H5T_NATIVE_INT;
+    hsize_t     dims[2] = { DATABUFFER_SIZE, DATABUFFER_SIZE };
+    int        *buf = NULL;
+    int         i = 0;
+    int         j = 0;
+
+    TESTING("Mirror open and dataset writing");
+
+    /* Create FAPL for Splitter[sec2|mirror]
+     */
+    fapl_id = create_mirroring_split_fapl("basic_write", &names);
+    if (H5I_INVALID_HID == fapl_id) {
+        TEST_ERROR;
+    }
+
+    /* Prepare data to be written
+     */
+    buf = (int *)HDmalloc(DATABUFFER_SIZE * DATABUFFER_SIZE * sizeof(int));
+    if (NULL == buf) {
+        TEST_ERROR;
+    }
+    for (i = 0; i < DATABUFFER_SIZE; i++) {
+        for (j = 0; j < DATABUFFER_SIZE; j++) {
+            int k = i * DATABUFFER_SIZE + j;
+            buf[k] = k;
+        }
+    }
+
+    /* -------------------- */
+    /* TEST: Create and Close */
+
+    file_id = H5Fcreate(names.rw, H5F_ACC_TRUNC, H5P_DEFAULT, fapl_id);
+    if (H5I_INVALID_HID == file_id) {
+        TEST_ERROR;
+    }
+    if (H5Fclose(file_id) == FAIL) {
+        TEST_ERROR;
+    }
+    file_id = H5I_INVALID_HID;
+
+
+    /* -------------------- */
+    /* TEST: Repoen and Write */
+
+    file_id = H5Fopen(names.rw, H5F_ACC_RDWR, fapl_id);
+    if (H5I_INVALID_HID == file_id) {
+        TEST_ERROR;
+    }
+
+    dspace_id = H5Screate_simple(2, dims, NULL);
+    if (H5I_INVALID_HID == dspace_id) {
+        TEST_ERROR;
+    }
+    dset_id = H5Dcreate2(file_id, "dataset", dtype_id, dspace_id, H5P_DEFAULT,
+            H5P_DEFAULT, H5P_DEFAULT);
+    if (H5I_INVALID_HID == dset_id) {
+        TEST_ERROR;
+    }
+
+    if (H5Dwrite(dset_id, dtype_id, H5S_ALL, H5S_ALL, H5P_DEFAULT, buf)
+        == FAIL)
+    {
+        TEST_ERROR;
+    }
+
+    /* -------------------- */
+    /* Standard cleanup */
+
+    HDfree(buf);
+    buf = NULL;
+    if (H5Dclose(dset_id) == FAIL) {
+        TEST_ERROR;
+    }
+    if (H5Sclose(dspace_id) == FAIL) {
+        TEST_ERROR;
+    }
+    if (H5Fclose(file_id) == FAIL) {
+        TEST_ERROR;
+    }
+    if (fapl_id != H5P_DEFAULT && fapl_id > 0) {
+        if (H5Pclose(fapl_id) == FAIL) {
+            TEST_ERROR;
+        }
+    }
+
+    /* -------------------- */
+    /* TEST: Verify that the R/W and W/O files are identical */
+
+    if (h5_compare_file_bytes(names.rw, names.wo) < 0) {
+        TEST_ERROR;
+    }
+
+    PASSED();
+    return 0;
+
+error:
+    H5E_BEGIN_TRY{
+        (void)H5Fclose(file_id);
+        if (buf) {
+            HDfree(buf);
+        }
+        (void)H5Dclose(dset_id);
+        (void)H5Sclose(dspace_id);
+        if (fapl_id != H5P_DEFAULT && fapl_id > 0) {
+            (void)H5Pclose(fapl_id);
+        }
+    } H5E_END_TRY;
+    return -1;
+} /* end test_basic_dataset_write() */
+
+
+/* ---------------------------------------------------------------------------
+ * Function:    test_chunked_dataset_write
+ *
+ * Purpose:     Create and close files; repoen files and write a dataset,
+ *              close; compare files.
+ *
+ *              TODO: receive target IP from caller?
+ *
+ * Return:      Success: 0
+ *              Failure: -1
+ *
+ * Programmer:  Jacob Smith
+ *              2019
+ * ---------------------------------------------------------------------------
+ */
+static int
+test_chunked_dataset_write(void)
+{
+    struct mirrortest_filenames names;
+    hid_t       file_id = H5I_INVALID_HID;
+    hid_t       fapl_id = H5P_DEFAULT;
+
+    TESTING("Mirror open and dataset writing (chunked)");
+
+    /* Create FAPL for Splitter[sec2|mirror]
+     */
+    fapl_id = create_mirroring_split_fapl("chunked_write", &names);
+    if (H5I_INVALID_HID == fapl_id) {
+        TEST_ERROR;
+    }
+
+    /* -------------------- */
+    /* TEST: Create and Close */
+
+    file_id = H5Fcreate(names.rw, H5F_ACC_TRUNC, H5P_DEFAULT, fapl_id);
+    if (H5I_INVALID_HID == file_id) {
+        TEST_ERROR;
+    }
+    if (H5Fclose(file_id) == FAIL) {
+        TEST_ERROR;
+    }
+    file_id = H5I_INVALID_HID;
+
+    /* -------------------- */
+    /* TEST: Reopen and Write */
+
+    file_id = H5Fopen(names.rw, H5F_ACC_RDWR, fapl_id);
+    if (H5I_INVALID_HID == file_id) {
+        TEST_ERROR;
+    }
+
+    /* Write datasets to file
+     */
+    if (create_datasets(file_id, 0, MAX_DSET_COUNT) == FAIL) {
+        TEST_ERROR;
+    }
+
+    /* Close to 'flush to disk', and reopen file
+     */
+    if (H5Fclose(file_id) == FAIL) {
+        TEST_ERROR;
+    }
+    file_id = H5I_INVALID_HID;
+
+    /* Reopen file
+     */
+    file_id = H5Fopen(names.rw, H5F_ACC_RDWR, fapl_id);
+    if (H5I_INVALID_HID == file_id) {
+        TEST_ERROR;
+    }
+
+    /* Verify written data integrity
+     */
+    if (verify_datasets(file_id, 0, MAX_DSET_COUNT) == FAIL) {
+        TEST_ERROR;
+    }
+
+    /* -------------------- */
+    /* Standard cleanup */
+
+    if (H5Fclose(file_id) == FAIL) {
+        TEST_ERROR;
+    }
+    file_id = H5I_INVALID_HID;
+    if (fapl_id != H5P_DEFAULT && fapl_id > 0) {
+        if (H5Pclose(fapl_id) == FAIL) {
+            TEST_ERROR;
+        }
+        fapl_id = H5I_INVALID_HID;
+    }
+
+    /* -------------------- */
+    /* TEST: Verify that the R/W and W/O files are identical */
+
+    if (h5_compare_file_bytes(names.rw, names.wo) < 0) {
+        TEST_ERROR;
+    }
+
+    PASSED();
+    return 0;
+
+error:
+    H5E_BEGIN_TRY {
+        (void)H5Fclose(file_id);
+        if (fapl_id != H5P_DEFAULT && fapl_id > 0) {
+            (void)H5Pclose(fapl_id);
+        }
+    } H5E_END_TRY;
+    return -1;
+} /* end test_chunked_dataset_write() */
+
+
+/* ---------------------------------------------------------------------------
+ * Function:    test_on_disk_zoo
+ *
+ * Purpose:     Verify that the mirror can handle the passing of all the
+ *              various on-disk data structures over the wire, as implemented
+ *              in genall5.c:create_zoo().
+ *
+ *              TODO: receive target IP from caller?
+ *
+ * Return:      Success: 0
+ *              Failure: -1
+ *
+ * Programmer:  Jacob Smith
+ *              2019
+ * ---------------------------------------------------------------------------
+ */
+static int
+test_on_disk_zoo(void)
+{
+    const char  grp_name[] = "/only";
+    struct mirrortest_filenames names;
+    hid_t       file_id = H5I_INVALID_HID;
+    hid_t       grp_id  = H5I_INVALID_HID;
+    hid_t       fapl_id = H5P_DEFAULT;
+
+    TESTING("'Zoo' of on-disk structures");
+
+    /* Create FAPL for Splitter[sec2|mirror]
+     */
+    fapl_id = create_mirroring_split_fapl("zoo", &names);
+    if (H5I_INVALID_HID == fapl_id) {
+        TEST_ERROR;
+    }
+
+    /* -------------------- */
+    /* TEST: Create file    */
+    file_id = H5Fcreate(names.rw, H5F_ACC_TRUNC, H5P_DEFAULT, fapl_id);
+    if (H5I_INVALID_HID == file_id) {
+        TEST_ERROR;
+    }
+
+    grp_id = H5Gcreate2(file_id, grp_name, H5P_DEFAULT, H5P_DEFAULT,
+            H5P_DEFAULT);
+    if (grp_id == H5I_INVALID_HID) {
+        TEST_ERROR;
+    }
+
+    /* Create datasets in file, close (flush) and reopen, validate.
+     * Use of ( pass ) a conceit required for using create_ and validate_zoo()
+     * from cache_common and/or genall5.
+     */
+
+    if ( pass ) {
+        create_zoo(file_id, grp_name, 0);
+    }
+    if ( pass ) {
+        if (H5Fclose(file_id) == FAIL) {
+            TEST_ERROR;
+        }
+        file_id = H5Fopen(names.rw, H5F_ACC_RDWR, fapl_id);
+        if (H5I_INVALID_HID == file_id) {
+            TEST_ERROR;
+        }
+    }
+    if ( pass ) {
+        validate_zoo(file_id, grp_name, 0); /* sanity-check */
+    }
+    if ( !pass ) {
+        HDprintf(failure_mssg);
+        TEST_ERROR;
+    }
+
+    /* -------------------- */
+    /* Standard cleanup */
+
+    if (fapl_id != H5P_DEFAULT && fapl_id >= 0) {
+        if (H5Pclose(fapl_id) == FAIL) {
+            TEST_ERROR;
+        }
+    }
+    if (H5Gclose(grp_id) == FAIL) {
+        TEST_ERROR;
+    }
+    if (H5Fclose(file_id) == FAIL) {
+        TEST_ERROR;
+    }
+
+    /* -------------------- */
+    /* TEST: Verify that the R/W and W/O files are identical */
+
+    if (h5_compare_file_bytes(names.rw, names.wo) < 0) {
+        TEST_ERROR;
+    }
+
+    PASSED();
+    return 0;
+
+error:
+    H5E_BEGIN_TRY {
+        (void)H5Fclose(file_id);
+        (void)H5Gclose(grp_id);
+        if (fapl_id != H5P_DEFAULT && fapl_id > 0) {
+            (void)H5Pclose(fapl_id);
+        }
+    } H5E_END_TRY;
+    return -1;
+} /* end test_on_disk_zoo() */
+
+
+/* ---------------------------------------------------------------------------
+ * Function:    test_vanishing_datasets
+ *
+ * Purpose:     Verify behavior when writing to a file where data is deleted.
+ *
+ *              Each dataset is populated with the value of its suffix
+ *              (dset5 is all fives).
+ *
+ *              Opens 0..15 create one new dataset each, '/dset[i]'.
+ *              Opens 3..18 delete '/dset[1-3]'
+ *
+ *              Should end with no data in file.
+ *
+ * Return:      Success:  0
+ *              Failure: -1
+ *
+ * Programmer:  Jacob Smith
+ *              2019
+ * ---------------------------------------------------------------------------
+ */
+static int
+test_vanishing_datasets(void)
+{
+    struct mirrortest_filenames names;
+    hid_t       file_id = H5I_INVALID_HID;
+    hid_t       fapl_id = H5I_INVALID_HID;
+    hid_t       dset_id = H5I_INVALID_HID;
+    hid_t       dspace_id = H5I_INVALID_HID;
+    hid_t       mirror_fapl_id = H5I_INVALID_HID;
+    hsize_t     dims[2] = {DATABUFFER_SIZE, DATABUFFER_SIZE};
+    uint32_t    buf[DATABUFFER_SIZE][DATABUFFER_SIZE]; /* consider malloc? */
+    H5G_info_t  group_info;
+    unsigned int        i, j, k;
+    const unsigned int  max_loops = 20;
+    const unsigned int  max_at_one_time = 3;
+
+    TESTING("Vanishing Datasets");
+
+    /* -------------------- */
+    /* Set up recurrent data (FAPL, dataspace) */
+
+    /* Create FAPL for Splitter[sec2|mirror]
+     */
+    fapl_id = create_mirroring_split_fapl("vanishing", &names);
+    if (H5I_INVALID_HID == fapl_id) {
+        TEST_ERROR;
+    }
+
+    dspace_id = H5Screate_simple(2, dims, NULL);
+    if (dspace_id < 0) {
+        TEST_ERROR;
+    }
+
+    /* create file */
+    file_id = H5Fcreate(names.rw, H5F_ACC_TRUNC, H5P_DEFAULT, fapl_id);
+    if (H5I_INVALID_HID == file_id) {
+        TEST_ERROR;
+    }
+
+    for (i=0; i < max_loops; i++) {
+        char namebuf[DSET_NAME_LEN + 1];
+
+        /* deleting datasets */
+        if (i >= max_at_one_time) {
+            if (HDsnprintf(namebuf, DSET_NAME_LEN, "/dset%02d",
+                    (i - max_at_one_time) )
+                > DSET_NAME_LEN)
+            {
+                TEST_ERROR;
+            }
+            if (H5Ldelete(file_id, namebuf, H5P_DEFAULT) < 0) {
+                TEST_ERROR;
+            }
+        } /* end if deleting a dataset */
+
+        /* writing datasets */
+        if (i < (max_loops - max_at_one_time)) {
+            if (HDsnprintf(namebuf, DSET_NAME_LEN, "/dset%02d", i)
+                > DSET_NAME_LEN)
+            {
+                TEST_ERROR;
+            }
+            dset_id = H5Dcreate2(file_id, namebuf, H5T_STD_U32LE, dspace_id,
+                    H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
+            if (H5I_INVALID_HID == dset_id) {
+                TEST_ERROR;
+            }
+
+            for (j=0; j < DATABUFFER_SIZE; j++) {
+                for (k=0; k < DATABUFFER_SIZE; k++) {
+                    buf[j][k] = (uint32_t)i;
+                }
+            }
+
+            if (H5Dwrite(dset_id, H5T_STD_U32LE, H5S_ALL, H5S_ALL, H5P_DEFAULT,
+                    buf)
+                < 0)
+            {
+                TEST_ERROR;
+            }
+
+            if (H5Dclose(dset_id) < 0) {
+                TEST_ERROR;
+            }
+            dset_id = H5I_INVALID_HID;
+        } /* end if writing a dataset */
+
+    } /* end for dataset create-destroy cycles */
+
+    if (H5Fclose(file_id) < 0) {
+        TEST_ERROR;
+    }
+    file_id = H5I_INVALID_HID;
+
+    /* verify there are no datasets in file */
+    file_id = H5Fopen(names.rw, H5F_ACC_RDONLY, H5P_DEFAULT);
+    if (file_id < 0) {
+        TEST_ERROR;
+    }
+    if (H5Gget_info(file_id, &group_info) < 0) {
+        TEST_ERROR;
+    }
+    if (group_info.nlinks > 0) {
+        HDfprintf(stderr, "links in rw file: %d\n", group_info.nlinks);
+        HDfflush(stderr);
+        TEST_ERROR;
+    }
+    if (H5Fclose(file_id) < 0) {
+        TEST_ERROR;
+    }
+    file_id = H5Fopen(names.wo, H5F_ACC_RDONLY, H5P_DEFAULT);
+    if (file_id < 0) {
+        TEST_ERROR;
+    }
+    if (H5Gget_info(file_id, &group_info) < 0) {
+        TEST_ERROR;
+    }
+    if (group_info.nlinks > 0) {
+        HDfprintf(stderr, "links in wo file: %d\n", group_info.nlinks);
+        HDfflush(stderr);
+        TEST_ERROR;
+    }
+    if (H5Fclose(file_id) < 0) {
+        TEST_ERROR;
+    }
+    file_id = H5I_INVALID_HID;
+
+    if (h5_compare_file_bytes(names.rw, names.wo) < 0)
+        TEST_ERROR;
+
+    /* -------------------- */
+    /* Teardown */
+
+    if (H5Sclose(dspace_id) < 0) {
+        TEST_ERROR;
+    }
+    if (H5Pclose(fapl_id) < 0) {
+        TEST_ERROR;
+    }
+
+    PASSED();
+    return 0;
+
+error:
+    H5E_BEGIN_TRY {
+        if (mirror_fapl_id != H5I_INVALID_HID) {
+            H5Pclose(mirror_fapl_id);
+        }
+        if (fapl_id != H5I_INVALID_HID) {
+            H5Pclose(fapl_id);
+        }
+        if (file_id != H5I_INVALID_HID) {
+            H5Fclose(file_id);
+        }
+        if (dset_id != H5I_INVALID_HID) {
+            H5Dclose(dset_id);
+        }
+        if (dspace_id != H5I_INVALID_HID) {
+            H5Sclose(dspace_id);
+        }
+    } H5E_END_TRY;
+    return -1;
+} /* test_vanishing_datasets() */
+
+
+/* ---------------------------------------------------------------------------
+ * Function:    test_concurrent_access
+ *
+ * Purpose:     Verify that more than one file may be opened at a time.
+ *
+ *              TODO: receive target IP from caller?
+ *
+ * Return:      Success: 0
+ *              Failure: -1
+ *
+ * Programmer:  Jacob Smith
+ *              2020-03-09
+ * ---------------------------------------------------------------------------
+ */
+static int
+test_concurrent_access(void)
+{
+    struct file_bundle {
+        struct mirrortest_filenames names;
+        hid_t dset_id;
+        hid_t fapl_id;
+        hid_t file_id;
+    } bundle[CONCURRENT_COUNT];
+    hid_t       dspace_id = H5I_INVALID_HID;
+    hid_t       dtype_id = H5T_NATIVE_INT;
+    hsize_t     dims[2] = { DATABUFFER_SIZE, DATABUFFER_SIZE };
+    int        *buf = NULL;
+    int         i = 0;
+    int         j = 0;
+
+    TESTING("Concurrent opened mirrored files");
+
+    /* blank bundle */
+    for (i = 0; i < CONCURRENT_COUNT; i++) {
+        bundle[i].dset_id = H5I_INVALID_HID;
+        bundle[i].fapl_id = H5I_INVALID_HID;
+        bundle[i].file_id = H5I_INVALID_HID;
+        *bundle[i].names.rw = '\0';
+        *bundle[i].names.wo = '\0';
+        *bundle[i].names.log = '\0';
+    }
+
+    /* Create FAPL for Splitter[sec2|mirror]
+     */
+    for (i = 0; i < CONCURRENT_COUNT; i++) {
+        char _name[16] = "";
+        hid_t _fapl_id = H5I_INVALID_HID;
+        HDsnprintf(_name, 15, "concurrent%d", i);
+        _fapl_id = create_mirroring_split_fapl(_name, &bundle[i].names);
+        if (H5I_INVALID_HID == _fapl_id) {
+            TEST_ERROR;
+        }
+        bundle[i].fapl_id = _fapl_id;
+    }
+
+    /* Prepare data to be written
+     */
+    buf = (int *)HDmalloc(DATABUFFER_SIZE * DATABUFFER_SIZE * sizeof(int));
+    if (NULL == buf) {
+        TEST_ERROR;
+    }
+    for (i = 0; i < DATABUFFER_SIZE; i++) {
+        for (j = 0; j < DATABUFFER_SIZE; j++) {
+            int k = i * DATABUFFER_SIZE + j;
+            buf[k] = k;
+        }
+    }
+
+    /* Prepare generic dataspace
+     */
+    dspace_id = H5Screate_simple(2, dims, NULL);
+    if (H5I_INVALID_HID == dspace_id) {
+        TEST_ERROR;
+    }
+
+    /* -------------------- */
+    /* TEST: Create file and open elements */
+
+    for (i = 0; i < CONCURRENT_COUNT; i++) {
+        hid_t _file_id = H5I_INVALID_HID;
+        hid_t _dset_id = H5I_INVALID_HID;
+
+        _file_id = H5Fcreate(bundle[i].names.rw, H5F_ACC_TRUNC, H5P_DEFAULT,
+                bundle[i].fapl_id);
+        if (H5I_INVALID_HID == _file_id) {
+            TEST_ERROR;
+        }
+
+        bundle[i].file_id  = _file_id;
+
+        _dset_id = H5Dcreate2(_file_id, "dataset", dtype_id, dspace_id,
+                H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
+        if (H5I_INVALID_HID == _dset_id) {
+            TEST_ERROR;
+        }
+        bundle[i].dset_id = _dset_id;
+    }
+
+    /* -------------------- */
+    /* TEST: Write to files */
+
+    for (i = 0; i < CONCURRENT_COUNT; i++) {
+        if (H5Dwrite(bundle[i].dset_id, dtype_id, H5S_ALL, H5S_ALL,
+                H5P_DEFAULT, buf)
+            == FAIL)
+        {
+            TEST_ERROR;
+        }
+    }
+
+    /* -------------------- */
+    /* TEST: Close elements  */
+
+    for (i = 0; i < CONCURRENT_COUNT; i++) {
+        if (H5Dclose(bundle[i].dset_id) == FAIL) {
+            TEST_ERROR;
+        }
+        if (H5Fclose(bundle[i].file_id) == FAIL) {
+            TEST_ERROR;
+        }
+        if (H5Pclose(bundle[i].fapl_id) == FAIL) {
+            TEST_ERROR;
+        }
+    }
+
+    /* -------------------- */
+    /* Standard cleanup */
+
+    HDfree(buf);
+    buf = NULL;
+    if (H5Sclose(dspace_id) == FAIL) {
+        TEST_ERROR;
+    }
+
+    /* -------------------- */
+    /* TEST: Verify that the R/W and W/O files are identical */
+
+    for (i = 0; i < CONCURRENT_COUNT; i++) {
+        if (h5_compare_file_bytes(bundle[i].names.rw, bundle[i].names.wo) < 0) {
+            TEST_ERROR;
+        }
+    }
+
+    PASSED();
+    return 0;
+
+error:
+    H5E_BEGIN_TRY{
+        if (buf) {
+            HDfree(buf);
+        }
+        (void)H5Sclose(dspace_id);
+        for (i = 0; i < CONCURRENT_COUNT; i++) {
+            (void)H5Dclose(bundle[i].dset_id);
+            (void)H5Fclose(bundle[i].file_id);
+            (void)H5Pclose(bundle[i].fapl_id);
+        }
+    } H5E_END_TRY;
+    return -1;
+} /* end test_concurrent_access() */
+
+
+/* ---------------------------------------------------------------------------
+ * Function:    main
+ *
+ * Purpose:     Run tests.
+ *
+ * Return:      Success: 0
+ *              Failure: 1
+ *
+ * Programmer:  Jacob Smith
+ *              2019
+ * ---------------------------------------------------------------------------
+ */
+int
+main(void)
+{
+    int nerrors = 0;
+
+    h5_reset();
+
+    g_log_stream = stdout; /* default debug/logging output stream */
+
+    HDprintf("Testing Mirror VFD functionality.\n");
+
+    /* -------------------- */
+    /* SETUP */
+
+    /* Create directories for test-generated .h5 files
+     */
+    if (nerrors == 0) {
+        if ((HDmkdir(MIRROR_RW_DIR, (mode_t)0755) < 0) && (errno != EEXIST)) {
+            nerrors++;
+        }
+    }
+    if (nerrors == 0) {
+        if ((HDmkdir(MIRROR_WO_DIR, (mode_t)0755) < 0) && (errno != EEXIST)) {
+            nerrors++;
+        }
+    }
+
+    /* -------------------- */
+    /* TESTS */
+    /* Tests return negative values; `-=' increments nerrors count */
+
+    if (nerrors == 0) {
+        nerrors -= test_fapl_configuration();
+        nerrors -= test_xmit_encode_decode();
+        nerrors -= test_create_and_close();
+        nerrors -= test_basic_dataset_write();
+        nerrors -= test_chunked_dataset_write();
+        nerrors -= test_on_disk_zoo();
+        nerrors -= test_vanishing_datasets();
+        nerrors -= test_concurrent_access();
+    }
+
+    if (nerrors) {
+        HDprintf("***** %d Mirror VFD TEST%s FAILED! *****\n",
+                nerrors, nerrors > 1 ? "S" : "");
+        return EXIT_FAILURE;
+    }
+
+    HDprintf("All Mirror Virtual File Driver tests passed.\n");
+    return EXIT_SUCCESS;
+} /* end main() */
+
+#else /* H5_HAVE_MIRROR_VFD */
+
+int
+main(void)
+{
+    h5_reset();
+    HDprintf("Testing Mirror VFD functionality.\n");
+    HDprintf("SKIPPED - Mirror VFD not built.\n");
+    return EXIT_SUCCESS;
+}
+
+#endif /* H5_HAVE_MIRROR_VFD */
+
+
diff --git a/test/test_mirror.sh.in b/test/test_mirror.sh.in
new file mode 100644
index 0000000..3fdc673
--- /dev/null
+++ b/test/test_mirror.sh.in
@@ -0,0 +1,100 @@
+#! /bin/bash
+#
+# Copyright by The HDF Group.
+# All rights reserved.
+#
+# This file is part of HDF5.  The full HDF5 copyright notice, including
+# terms governing use, modification, and redistribution, is contained in
+# the COPYING file, which can be found at the root of the source code
+# distribution tree, or in https://support.hdfgroup.org/ftp/HDF5/releases.
+# If you do not have access to either file, you may request a copy from
+# help@hdfgroup.org.
+#
+# Tests for the Mirror VFD feature.
+#
+# Created:
+#   Jacob Smith, 2019-12-30
+
+###############################################################################
+## test parameters
+###############################################################################
+
+nerrors=0
+
+SERVER_VERBOSITY="--verbosity=1"
+SERVER_PORT="--port=3000"
+
+
+###############################################################################
+## Main
+###############################################################################
+
+## TODO: arguments for main port, port range, verbosity?
+# Parse options (none accepted at this time)
+while [ $# -gt 0 ]; do
+    case "$1" in
+    *)  # unknown option
+        echo "$0: Unknown option ($1)"
+        exit 1
+        ;;
+    esac
+done
+
+
+
+RUN_DIR=mirror_vfd_test
+MIRROR_UTILS=../utils/mirror_vfd # TODO: presupposes from test/
+
+mkdir $RUN_DIR
+
+# Copy program files into dedicated test directory
+for FILE in $MIRROR_UTILS/mirror_* ; do
+    case "$FILE" in
+        *.o) continue ;; # Don't copy .o files
+    esac
+    cp $FILE $RUN_DIR
+done
+cp mirror_vfd $RUN_DIR
+
+# With the --disable-shared option, program files are built in their main
+# directories; otherwise they are built in dir/.libs with a corresponding
+# wrapper script. Copy these libs builds if appropriate.
+if [ -f $MIRROR_UTILS/.libs/mirror_server ] ; then
+    RUN_LIBS=$RUN_DIR/.libs
+    mkdir $RUN_LIBS
+    for FILE in $MIRROR_UTILS/.libs/mirror_* ; do
+        case "$FILE" in
+            *.o) continue ;; # Don't copy .o files
+        esac
+        cp $FILE $RUN_LIBS
+    done
+    cp .libs/mirror_vfd $RUN_LIBS
+fi
+
+cd $RUN_DIR
+
+echo "Launching Mirror Server"
+SERVER_ARGS="$SERVER_PORT $SERVER_VERBOSITY"
+./mirror_server $SERVER_ARGS &
+
+./mirror_vfd
+nerrors=$?
+
+echo "Stopping Mirror Server"
+./mirror_server_halten_sie $SERVER_PORT
+
+###############################################################################
+## Report and exit
+###############################################################################
+cd ..
+if test $nerrors -eq 0 ; then
+    echo "Mirror VFD tests passed."
+    if test -z "$HDF5_NOCLEANUP" ; then
+        rm -rf $RUN_DIR
+    fi
+    exit 0
+else
+    echo "Mirror VFD tests FAILED."
+    exit 1
+fi
+
diff --git a/test/use.h b/test/use.h
index 54d9b26..e5eced2 100644
--- a/test/use.h
+++ b/test/use.h
@@ -16,48 +16,46 @@
 #include "h5test.h"
 
 /* Macro definitions */
-#define Hgoto_error(val)	{ret_value=val; goto done;}
-#define Hgoto_done		{goto done;}
-#define Chunksize_DFT		256	/* chunksize default */
-#define ErrorReportMax		10	/* max number of errors reported */
+#define Hgoto_error(val)        {ret_value=val; goto done;}
+#define Hgoto_done              {goto done;}
+#define Chunksize_DFT           256     /* chunksize default */
+#define ErrorReportMax          10      /* max number of errors reported */
 /* these two definitions must match each other */
-#define UC_DATATYPE		H5T_NATIVE_SHORT    /* use case HDF5 data type */
-#define UC_CTYPE		short		    /* use case C data type */
-#define UC_RANK			3		    /* use case dataset rank */
+#define UC_DATATYPE             H5T_NATIVE_SHORT  /* use case HDF5 data type */
+#define UC_CTYPE                short   /* use case C data type */
+#define UC_RANK                 3       /* use case dataset rank */
 
 /* Name of message file that is sent by the writer */
 #define WRITER_MESSAGE          "USE_WRITER_MESSAGE"
 
 /* type declarations */
 typedef enum part_t {
-    UC_READWRITE	=0,	/* both writer and reader */
-    UC_WRITER,			/* writer only */
-    UC_READER			/* reader only */
+    UC_READWRITE = 0,           /* both writer and reader */
+    UC_WRITER,                  /* writer only */
+    UC_READER                   /* reader only */
 } part_t;
 
 typedef struct options_t {
-    hsize_t chunksize;		/* chunks are chunksize^2 planes	*/
-    hsize_t chunkplanes;	/* number of planes per chunk, default 1 */
+    hsize_t chunksize;          /* chunks are chunksize^2 planes         */
+    hsize_t chunkplanes;        /* number of planes per chunk, default 1 */
     hsize_t chunkdims[UC_RANK]; /* chunk dims is (chunkplan, chunksize, chunksize) */
     hsize_t dims[UC_RANK];      /* dataset initial dims */
     hsize_t max_dims[UC_RANK];  /* dataset max dims */
-    hsize_t nplanes;		/* number of planes to write, default proportional to chunksize */
-    char *filename;		/* use case data filename		*/
-    part_t launch;		/* launch writer, reader or both	*/
-    hbool_t use_swmr;           /* use swmr open (1) or not 		*/
-    int iterations;		/* iterations, default 1		*/
+    hsize_t nplanes;            /* number of planes to write, default proportional to chunksize */
+    char *filename;             /* use case data filename               */
+    part_t launch;              /* launch writer, reader or both        */
+    hbool_t use_swmr;           /* use swmr open (1) or not             */
+    int iterations;             /* iterations, default 1                */
+    hid_t fapl_id;              /* instance-specific FAPL ID            */
+    char *progname;             /* Program name (used in usage and dset name) */
 } options_t;
 
-/* global variables declarations */
-extern options_t UC_opts;	/* Use Case Options */
-extern const char *progname_g;	/* Program name */
-
 /* prototype declarations */
-int parse_option(int argc, char * const argv[]);
-int setup_parameters(int argc, char * const argv[]);
-void show_parameters(void);
+int parse_option(int argc, char * const argv[], options_t * opts);
+int setup_parameters(int argc, char * const argv[], options_t * opts);
+void show_parameters(options_t * opts);
 void usage(const char *prog);
-int create_uc_file(void);
-int write_uc_file(hbool_t tosend, hid_t fid);
-int read_uc_file(hbool_t towait);
+int create_uc_file(options_t * opts);
+int write_uc_file(hbool_t tosend, hid_t file_id, options_t * opts);
+int read_uc_file(hbool_t towait, options_t * opts);
 
diff --git a/test/use_append_chunk.c b/test/use_append_chunk.c
index 6b34f1e..35594cf 100644
--- a/test/use_append_chunk.c
+++ b/test/use_append_chunk.c
@@ -11,7 +11,7 @@
  * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
 
 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
- * Use Case 1.7	Appending a single chunk
+ * Use Case 1.7 Appending a single chunk
  * Description:
  *     Appending a single chunk of raw data to a dataset along an unlimited
  *     dimension within a pre-created file and reading the new data back.
@@ -24,35 +24,36 @@
  * Level:
  *     User Level
  * Guarantees:
- *     o	Readers will see the modified dimension sizes after the Writer
- * 	finishes HDF5 metadata updates and issues H5Fflush or H5Oflush calls.
- *     o	Readers will see newly appended data after the Writer finishes
- * 	the flush operation.
- * 
+ *     o Readers will see the modified dimension sizes after the Writer
+ *       finishes HDF5 metadata updates and issues H5Fflush or H5Oflush calls.
+ *     o Readers will see newly appended data after the Writer finishes
+ *       the flush operation.
+ *
  * Preconditions:
- *     o	Readers are not allowed to modify the file.  o	 All datasets
- * 	that are modified by the Writer exist when the Writer opens the file.
- *     o	All datasets that are modified by the Writer exist when a Reader
- * 	opens the file.  o	 Data is written by a hyperslab contained in
- * 	one chunk.
- * 
+ *     o Readers are not allowed to modify the file.
+ *     o All datasets that are modified by the Writer exist when the Writer
+ *       opens the file.
+ *     o All datasets that are modified by the Writer exist when a Reader
+ *       opens the file.
+ *     o Data is written by a hyperslab contained in one chunk.
+ *
  * Main Success Scenario:
- *     1.	An application creates a file with required objects (groups,
- * 	datasets, and attributes).
- *     2.	The Writer application opens the file and datasets in the file
- * 	and starts adding data along the unlimited dimension using a hyperslab
- * 	selection that corresponds to an HDF5 chunk.
- *     3.	A Reader opens the file and a dataset in a file, and queries
- * 	the sizes of the dataset; if the extent of the dataset has changed,
- * 	reads the appended data back.
- * 
+ *     1. An application creates a file with required objects (groups,
+ *        datasets, and attributes).
+ *     2. The Writer application opens the file and datasets in the file
+ *        and starts adding data along the unlimited dimension using a hyperslab
+ *        selection that corresponds to an HDF5 chunk.
+ *     3. A Reader opens the file and a dataset in a file, and queries
+ *        the sizes of the dataset; if the extent of the dataset has changed,
+ *        reads the appended data back.
+ *
  * Discussion points:
- *     1.	Since the new data is written to the file, and metadata update
- * 	operation of adding pointer to the newly written chunk is atomic and
- * 	happens after the chunk is on the disk, only two things may happen
- * 	to the Reader:
- * 	    o	The Reader will not see new data.
- * 	    o	The Reader will see all new data written by Writer.
+ *     1. Since the new data is written to the file, and metadata update
+ *        operation of adding pointer to the newly written chunk is atomic and
+ *        happens after the chunk is on the disk, only two things may happen
+ *        to the Reader:
+ *         o The Reader will not see new data.
+ *         o The Reader will see all new data written by Writer.
  * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
 
 /* Created: Albert Cheng, 2013/5/28 */
@@ -68,46 +69,43 @@
 
 #include "use.h"
 
-/* Global Variable definitions */
-options_t UC_opts;	/* Use Case Options */
-const char *progname_g="use_append_chunk";	/* program name */
+#define USE_APPEND_CHUNK_PROGNAME "use_append_chunk"
+
+static options_t UC_opts; /* Use Case Options */
 
 /* Setup parameters for the use case.
  * Return: 0 succeed; -1 fail.
  */
-int setup_parameters(int argc, char * const argv[])
+int
+setup_parameters(int argc, char * const argv[], options_t * opts)
 {
     /* use case defaults */
-    HDmemset(&UC_opts, 0, sizeof(options_t));
-    UC_opts.chunksize = Chunksize_DFT;
-    UC_opts.use_swmr = TRUE;	/* use swmr open */
-    UC_opts.iterations = 1;
-    UC_opts.chunkplanes = 1;
-
-    /* parse options */
-    if (parse_option(argc, argv) < 0)
-	return(-1);
-
-    /* set chunk dims */
-    UC_opts.chunkdims[0] = UC_opts.chunkplanes;
-    UC_opts.chunkdims[1] = UC_opts.chunkdims[2] = UC_opts.chunksize;
-
-    /* set dataset initial and max dims */
-    UC_opts.dims[0] = 0;
-    UC_opts.max_dims[0] = H5S_UNLIMITED;
-    UC_opts.dims[1] = UC_opts.dims[2] = UC_opts.max_dims[1] = UC_opts.max_dims[2] = UC_opts.chunksize;
-
-    /* set nplanes */
-    if (UC_opts.nplanes == 0)
-        UC_opts.nplanes = (hsize_t)UC_opts.chunksize;
-
-    /* show parameters and return */
-    show_parameters();
+    HDmemset(opts, 0, sizeof(options_t));
+    opts->chunksize = Chunksize_DFT;
+    opts->use_swmr = TRUE; /* use swmr open */
+    opts->iterations = 1;
+    opts->chunkplanes = 1;
+    opts->progname = USE_APPEND_CHUNK_PROGNAME;
+
+    if (parse_option(argc, argv, opts) < 0)
+        return(-1);
+
+    opts->chunkdims[0] = opts->chunkplanes;
+    opts->chunkdims[1] = opts->chunkdims[2] = opts->chunksize;
+
+    opts->dims[0] = 0;
+    opts->max_dims[0] = H5S_UNLIMITED;
+    opts->dims[1] = opts->dims[2] = opts->max_dims[1] = opts->max_dims[2] = opts->chunksize;
+
+    if (opts->nplanes == 0)
+        opts->nplanes = (hsize_t)opts->chunksize;
+
+    show_parameters(opts);
     return(0);
-}
+} /* setup_parameters() */
 
 
-/* Overall Algorithm: 
+/* Overall Algorithm:
  * Parse options from user;
  * Generate/pre-created test files needed and close it;
  * fork: child process becomes the reader process;
@@ -119,22 +117,20 @@ main(int argc, char *argv[])
 {
     pid_t childpid=0;
     pid_t mypid, tmppid;
-    int	child_status;
+    int child_status;
     int child_wait_option=0;
     int ret_value = 0;
     int child_ret_value;
     hbool_t send_wait = FALSE;
     hid_t fapl = -1;    /* File access property list */
     hid_t fid = -1;     /* File ID */
-    char *name;         /* Test file name */
 
-    /* initialization */
-    if (setup_parameters(argc, argv) < 0){
+    if (setup_parameters(argc, argv, &UC_opts) < 0) {
         Hgoto_error(1);
     }
 
     /* Determine the need to send/wait message file*/
-    if(UC_opts.launch == UC_READWRITE) {
+    if (UC_opts.launch == UC_READWRITE) {
         HDunlink(WRITER_MESSAGE);
         send_wait = TRUE;
     }
@@ -144,38 +140,63 @@ main(int argc, char *argv[])
     /* UC_WRITER:    create datafile, skip reader, launch writer.    */
     /* UC_READER:    skip create, launch reader, exit.               */
     /* ==============================================================*/
-    /* ============*/
+    /* =========== */
     /* Create file */
-    /* ============*/
-    if (UC_opts.launch != UC_READER){
+    /* =========== */
+    if (UC_opts.launch != UC_READER) {
         HDprintf("Creating skeleton data file for test...\n");
-        if (create_uc_file() < 0){
+        if ((UC_opts.fapl_id = h5_fileaccess()) < 0) {
+            HDfprintf(stderr, "can't create creation FAPL\n");
+            Hgoto_error(1);
+        }   
+        if (H5Pset_libver_bounds(UC_opts.fapl_id, H5F_LIBVER_LATEST, H5F_LIBVER_LATEST) < 0) {
+            HDfprintf(stderr, "can't set creation FAPL libver bounds\n");
+            Hgoto_error(1);
+        }
+        if (create_uc_file(&UC_opts) < 0) {
             HDfprintf(stderr, "***encounter error\n");
             Hgoto_error(1);
-        }else
+        } else {
             HDprintf("File created.\n");
+        }
+        /* Close FAPL to prevent issues with forking later */ 
+        if (H5Pclose(UC_opts.fapl_id) < 0) {
+            HDfprintf(stderr, "can't close creation FAPL\n");
+            Hgoto_error(1);
+        }
+        UC_opts.fapl_id = H5I_INVALID_HID;
     }
 
-    if (UC_opts.launch==UC_READWRITE){
-        /* fork process */
-        if((childpid = HDfork()) < 0) {
+    /* ============ */
+    /* Fork process */
+    /* ============ */
+    if (UC_opts.launch == UC_READWRITE) {
+        if ((childpid = HDfork()) < 0) {
             HDperror("fork");
             Hgoto_error(1);
-        };
-    };
+        }
+    }
     mypid = HDgetpid();
 
     /* ============= */
     /* launch reader */
     /* ============= */
-    if (UC_opts.launch != UC_WRITER){
+    if (UC_opts.launch != UC_WRITER) {
         /* child process launch the reader */
-        if(0 == childpid) {
+        if (0 == childpid) {
             HDprintf("%d: launch reader process\n", mypid);
-            if (read_uc_file(send_wait) < 0){
+            if ((UC_opts.fapl_id = h5_fileaccess()) < 0) {
+                HDfprintf(stderr, "can't create read FAPL\n");
+                HDexit(EXIT_FAILURE);
+            }
+            if (read_uc_file(send_wait, &UC_opts) < 0) {
                 HDfprintf(stderr, "read_uc_file encountered error\n");
                 HDexit(EXIT_FAILURE);
             }
+            if (H5Pclose(UC_opts.fapl_id) < 0) {
+                HDfprintf(stderr, "can't close read FAPL\n");
+                HDexit(EXIT_FAILURE);
+            }
             HDexit(EXIT_SUCCESS);
         }
     }
@@ -186,65 +207,63 @@ main(int argc, char *argv[])
     /* this process continues to launch the writer */
     HDprintf("%d: continue as the writer process\n", mypid);
 
-    name = UC_opts.filename;
-
-    /* Set file access proeprty list */
-    if((fapl = h5_fileaccess()) < 0)
+    if ((fapl = h5_fileaccess()) < 0) {
+        HDfprintf(stderr, "can't create write FAPL\n");
         Hgoto_error(1);
+    }
 
-    if(UC_opts.use_swmr)
-        if(H5Pset_libver_bounds(fapl, H5F_LIBVER_LATEST, H5F_LIBVER_LATEST) < 0)
+    if (UC_opts.use_swmr) {
+        if (H5Pset_libver_bounds(fapl, H5F_LIBVER_LATEST, H5F_LIBVER_LATEST) < 0) {
+            HDfprintf(stderr, "can't set write FAPL libver bounds\n");
             Hgoto_error(1);
+        }
+    }
 
-    /* Open the file */
-    if((fid = H5Fopen(name, H5F_ACC_RDWR | (UC_opts.use_swmr ? H5F_ACC_SWMR_WRITE : 0), fapl)) < 0) {
+    if ((fid = H5Fopen(UC_opts.filename, H5F_ACC_RDWR | (UC_opts.use_swmr ? H5F_ACC_SWMR_WRITE : 0), fapl)) < 0) {
         HDfprintf(stderr, "H5Fopen failed\n");
         Hgoto_error(1);
     }
 
-    if(write_uc_file(send_wait, fid) < 0) {
+    if (write_uc_file(send_wait, fid, &UC_opts) < 0) {
         HDfprintf(stderr, "write_uc_file encountered error\n");
         Hgoto_error(1);
     }
 
+    if (H5Fclose(fid) < 0) {
+        HDfprintf(stderr, "Failed to close write\n");
+        Hgoto_error(1);
+    }
+
+    if (H5Pclose(fapl) < 0) {
+        HDfprintf(stderr, "can't close write FAPL\n");
+        Hgoto_error(1);
+    }
+
     /* ================================================ */
     /* If readwrite, collect exit code of child process */
     /* ================================================ */
-    if (UC_opts.launch == UC_READWRITE){
-        if ((tmppid = HDwaitpid(childpid, &child_status, child_wait_option)) < 0){
+    if (UC_opts.launch == UC_READWRITE) {
+        if ((tmppid = HDwaitpid(childpid, &child_status, child_wait_option)) < 0) {
             HDperror("waitpid");
             Hgoto_error(1);
         }
 
-        /* Close the file */
-        if(H5Fclose(fid) < 0) {
-            HDfprintf(stderr, "Failed to close file id\n");
-            Hgoto_error(1);
-        }
-
-        /* Close the property list */
-        if(H5Pclose(fapl) < 0) {
-            HDfprintf(stderr, "Failed to close the property list\n");
-            Hgoto_error(1);
-        }
-
-        if (WIFEXITED(child_status)){
-            if ((child_ret_value=WEXITSTATUS(child_status)) != 0){
+        if (WIFEXITED(child_status)) {
+            if ((child_ret_value = WEXITSTATUS(child_status)) != 0) {
                 HDprintf("%d: child process exited with non-zero code (%d)\n",
                         mypid, child_ret_value);
                 Hgoto_error(2);
             }
-         } else {
-                HDprintf("%d: child process terminated abnormally\n", mypid);
-                Hgoto_error(2);
-         }
+        } else {
+            HDprintf("%d: child process terminated abnormally\n", mypid);
+            Hgoto_error(2);
+        }
     }
-    
+
 done:
-    /* Print result and exit */
-    if (ret_value != 0){
+    if (ret_value != 0) {
         HDprintf("Error(s) encountered\n");
-    }else{
+    } else {
         HDprintf("All passed\n");
     }
 
diff --git a/test/use_append_chunk_mirror.c b/test/use_append_chunk_mirror.c
new file mode 100644
index 0000000..6ee01c0
--- /dev/null
+++ b/test/use_append_chunk_mirror.c
@@ -0,0 +1,403 @@
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
+ * Copyright by The HDF Group.                                               *
+ * All rights reserved.                                                      *
+ *                                                                           *
+ * This file is part of HDF5.  The full HDF5 copyright notice, including     *
+ * terms governing use, modification, and redistribution, is contained in    *
+ * the COPYING file, which can be found at the root of the source code       *
+ * distribution tree, or in https://support.hdfgroup.org/ftp/HDF5/releases.  *
+ * If you do not have access to either file, you may request a copy from     *
+ * help@hdfgroup.org.                                                        *
+ * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+/* HACKED VERSION
+ * Demonstrate SWMR with a mirrored file.
+ *
+ * Must be built with SERVER_IP as the IP address of the target system
+ * with a running mirror server, and SERVER_PORT as the primary server port.
+ *
+ * In addition to the local file, 'shinano.h5' will be created on the remote
+ * system, mirroring the local file. The file location will be local to
+ * Server's/Writer's invocation directory.
+ *
+ * Template for demonstration purposes:
+ *
+ * # Launch mirror server on remote machine (in foreground to easily stop)
+ * REMOTE(1)$ ./mirror_server /path/to/mirror_worker
+ *
+ * # Launch chunk writer with plenty of chunks.
+ * LOCAL(1)$ ./use_append_chunk_mirror -l w -n 10000
+ *
+ * # Wait one second for files to be created.
+ *
+ * # Launch chunk readers on both files.
+ * LOCAL(2)$ ./use_append_chunk_mirror -l r -n 10000
+ * REMOTE(2)$ ./use_append_chunk_mirror -l r -n 10000 -f shinano.h5
+ *
+ * # Hard-stop the server.
+ * REMOTE(1)$ ^C
+ * # alt, softer shutdown using echo and nc
+ * echo "SHUTDOWN" | nc localhost 3000
+ */
+
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
+ * Use Case 1.7 Appending a single chunk
+ * Description:
+ *     Appending a single chunk of raw data to a dataset along an unlimited
+ *     dimension within a pre-created file and reading the new data back.
+ * Goal:
+ *     Read data appended by the Writer to a pre-existing dataset in a
+ *     file. The dataset has one or more unlimited dimensions. The data is
+ *     appended by a hyperslab that is contained in one chunk (for example,
+ *     appending 2-dim planes along the slowest changing dimension in the
+ *     3-dim dataset).
+ * Level:
+ *     User Level
+ * Guarantees:
+ *     o Readers will see the modified dimension sizes after the Writer
+ *       finishes HDF5 metadata updates and issues H5Fflush or H5Oflush calls.
+ *     o Readers will see newly appended data after the Writer finishes
+ *       the flush operation.
+ *
+ * Preconditions:
+ *     o Readers are not allowed to modify the file.
+ *     o All datasets that are modified by the Writer exist when the Writer
+ *       opens the file.
+ *     o All datasets that are modified by the Writer exist when a Reader
+ *       opens the file.
+ *     o Data is written by a hyperslab contained in one chunk.
+ *
+ * Main Success Scenario:
+ *     1. An application creates a file with required objects (groups,
+ *        datasets, and attributes).
+ *     2. The Writer application opens the file and datasets in the file
+ *        and starts adding data along the unlimited dimension using a hyperslab
+ *        selection that corresponds to an HDF5 chunk.
+ *     3. A Reader opens the file and a dataset in a file, and queries
+ *        the sizes of the dataset; if the extent of the dataset has changed,
+ *        reads the appended data back.
+ *
+ * Discussion points:
+ *     1. Since the new data is written to the file, and metadata update
+ *        operation of adding pointer to the newly written chunk is atomic and
+ *        happens after the chunk is on the disk, only two things may happen
+ *        to the Reader:
+ *         o The Reader will not see new data.
+ *         o The Reader will see all new data written by Writer.
+ * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+/* Created: Jacob Smith, 2019 */
+
+#include "use.h"
+
+/* This test uses many POSIX things that are not available on
+ * Windows. We're using a check for fork(2) here as a proxy for
+ * all POSIX/Unix/Linux things until this test can be made
+ * more platform-independent.
+ */
+#ifdef H5_HAVE_FORK
+
+#ifdef H5_HAVE_MIRROR_VFD
+
+#define THIS_PROGNAME "use_append_chunk_mirror"
+
+#define CONNECT_WITH_JELLY 0
+
+#if CONNECT_WITH_JELLY
+#define SERVER_IP "10.10.10.248" /* hard-coded IP address */
+#else
+#define SERVER_IP "127.0.0.1"    /* localhost */
+#endif /* CONNECT_WITH_JELLY */
+#define SERVER_PORT 3000         /* hard-coded port number */
+#define MIRROR_FILE_NAME "shinano.h5" /* hard-coded duplicate/mirror filename */
+
+static options_t UC_opts; /* Use Case Options */
+
+/* Setup parameters for the use case.
+ * Return: 0 succeed; -1 fail.
+ */
+int
+setup_parameters(int argc, char * const argv[], options_t * opts)
+{
+    /* use case defaults */
+    HDmemset(opts, 0, sizeof(options_t));
+    opts->chunksize = Chunksize_DFT;
+    opts->use_swmr = TRUE;
+    opts->iterations = 1;
+    opts->chunkplanes = 1;
+    opts->progname = THIS_PROGNAME;
+
+    if (parse_option(argc, argv, opts) < 0)
+        return(-1);
+
+    opts->chunkdims[0] = opts->chunkplanes;
+    opts->chunkdims[1] = opts->chunkdims[2] = opts->chunksize;
+
+    opts->dims[0] = 0;
+    opts->max_dims[0] = H5S_UNLIMITED;
+    opts->dims[1] = opts->dims[2] = opts->max_dims[1] = opts->max_dims[2] = opts->chunksize;
+
+    if (opts->nplanes == 0)
+        opts->nplanes = (hsize_t)opts->chunksize;
+
+    show_parameters(opts);
+    return(0);
+} /* setup_parameters() */
+
+
+/* Overall Algorithm:
+ * Parse options from user;
+ * Generate/pre-created test files needed and close it;
+ * fork: child process becomes the reader process;
+ *       while parent process continues as the writer process;
+ * both run till ending conditions are met.
+ */
+int
+main(int argc, char *argv[])
+{
+    pid_t childpid=0;
+    pid_t mypid, tmppid;
+    int child_status;
+    int child_wait_option=0;
+    int ret_value = 0;
+    int child_ret_value;
+    hbool_t send_wait = FALSE;
+    hid_t fid = -1;     /* File ID */
+    H5FD_mirror_fapl_t mirr_fa;
+    H5FD_splitter_vfd_config_t split_fa;
+    hid_t mirr_fapl_id = H5I_INVALID_HID;
+
+    if (setup_parameters(argc, argv, &UC_opts) < 0) {
+        Hgoto_error(1);
+    }
+
+    mirr_fa.magic          = H5FD_MIRROR_FAPL_MAGIC;
+    mirr_fa.version        = H5FD_MIRROR_CURR_FAPL_T_VERSION;
+    mirr_fa.handshake_port = SERVER_PORT;
+    HDstrncpy(mirr_fa.remote_ip, SERVER_IP, H5FD_MIRROR_MAX_IP_LEN);
+
+
+    split_fa.wo_fapl_id       = H5I_INVALID_HID;
+    split_fa.rw_fapl_id       = H5I_INVALID_HID;
+    split_fa.magic            = H5FD_SPLITTER_MAGIC;
+    split_fa.version          = H5FD_CURR_SPLITTER_VFD_CONFIG_VERSION;
+    split_fa.log_file_path[0] = '\0'; /* none */
+    split_fa.ignore_wo_errs   = FALSE;
+    HDstrncpy(split_fa.wo_path, MIRROR_FILE_NAME, H5FD_SPLITTER_PATH_MAX);
+
+    /* Determine the need to send/wait message file*/
+    if (UC_opts.launch == UC_READWRITE) {
+        HDunlink(WRITER_MESSAGE);
+        send_wait = TRUE;
+    }
+
+    /* ==============================================================*/
+    /* UC_READWRITE: create datafile, launch both reader and writer. */
+    /* UC_WRITER:    create datafile, skip reader, launch writer.    */
+    /* UC_READER:    skip create, launch reader, exit.               */
+    /* ==============================================================*/
+    /* =========== */
+    /* Create file */
+    /* =========== */
+    if (UC_opts.launch != UC_READER) {
+        HDprintf("Creating skeleton data file for test...\n");
+
+        /* Prepare mirror child driver */
+        mirr_fapl_id = H5Pcreate(H5P_FILE_ACCESS);
+        if (mirr_fapl_id == H5I_INVALID_HID) {
+            HDfprintf(stderr, "can't create creation mirror FAPL\n");
+            Hgoto_error(1);
+        }
+        if (H5Pset_fapl_mirror(mirr_fapl_id, &mirr_fa) < 0) {
+            HDfprintf(stderr, "can't set creation mirror FAPL\n");
+            H5Eprint2(H5E_DEFAULT, stdout);
+            Hgoto_error(1);
+        }
+
+        /* Prepare parent "splitter" driver in UC_opts */
+        split_fa.wo_fapl_id       = mirr_fapl_id;
+        split_fa.rw_fapl_id       = H5P_DEFAULT;
+        UC_opts.fapl_id = H5Pcreate(H5P_FILE_ACCESS);
+        if (UC_opts.fapl_id == H5I_INVALID_HID) {
+            HDfprintf(stderr, "can't create creation FAPL\n");
+            Hgoto_error(1);
+        }
+        if (H5Pset_fapl_splitter(UC_opts.fapl_id, &split_fa) < 0) {
+            HDfprintf(stderr, "can't set creation FAPL\n");
+            H5Eprint2(H5E_DEFAULT, stdout);
+            Hgoto_error(1);
+        }
+
+        if (H5Pset_libver_bounds(UC_opts.fapl_id, H5F_LIBVER_LATEST, H5F_LIBVER_LATEST) < 0) {
+            HDfprintf(stderr, "can't set creation FAPL libver bounds\n");
+            Hgoto_error(1);
+        }
+
+        /* Create file */
+        if (create_uc_file(&UC_opts) < 0) {
+            HDfprintf(stderr, "***encounter error\n");
+            Hgoto_error(1);
+        } else {
+            HDprintf("File created.\n");
+        }
+
+        /* Close FAPLs to prevent issues with forking later */
+        if (H5Pclose(UC_opts.fapl_id) < 0) {
+            HDfprintf(stderr, "can't close creation FAPL\n");
+            Hgoto_error(1);
+        }
+        UC_opts.fapl_id = H5I_INVALID_HID;
+        if (H5Pclose(mirr_fapl_id) < 0) {
+            HDfprintf(stderr, "can't close creation mirror FAPL\n");
+            Hgoto_error(1);
+        }
+        mirr_fapl_id = H5I_INVALID_HID;
+    }
+
+    /* ============ */
+    /* Fork process */
+    /* ============ */
+    if (UC_opts.launch == UC_READWRITE) {
+        if ((childpid = HDfork()) < 0) {
+            HDperror("fork");
+            Hgoto_error(1);
+        }
+    }
+    mypid = HDgetpid();
+
+    /* ============= */
+    /* launch reader */
+    /* ============= */
+    if (UC_opts.launch != UC_WRITER) {
+        /* child process -- launch the reader */
+        /* reader only opens the one file -- separate reader needed for mirrored file 'shinano.h5' */
+        if (0 == childpid) {
+            HDprintf("%d: launch reader process\n", mypid);
+
+            UC_opts.fapl_id = H5P_DEFAULT;
+            if (read_uc_file(send_wait, &UC_opts) < 0) {
+                HDfprintf(stderr, "read_uc_file encountered error (%d)\n", mypid);
+                HDexit(1);
+            }
+
+            HDexit(0);
+        }
+    }
+
+    /* ============= */
+    /* launch writer */
+    /* ============= */
+    /* this process continues to launch the writer */
+    HDprintf("%d: continue as the writer process\n", mypid);
+
+    /* Prepare mirror child driver */
+    mirr_fapl_id = H5Pcreate(H5P_FILE_ACCESS);
+    if (mirr_fapl_id == H5I_INVALID_HID) {
+        HDfprintf(stderr, "can't create creation mirror FAPL\n");
+        Hgoto_error(1);
+    }
+    if (H5Pset_fapl_mirror(mirr_fapl_id, &mirr_fa) < 0) {
+        HDfprintf(stderr, "can't set creation mirror FAPL\n");
+        H5Eprint2(H5E_DEFAULT, stdout);
+        Hgoto_error(1);
+    }
+
+    /* Prepare parent "splitter" driver in UC_opts */
+    split_fa.wo_fapl_id       = mirr_fapl_id;
+    split_fa.rw_fapl_id       = H5P_DEFAULT;
+    UC_opts.fapl_id = H5Pcreate(H5P_FILE_ACCESS);
+    if (UC_opts.fapl_id == H5I_INVALID_HID) {
+        HDfprintf(stderr, "can't create creation FAPL\n");
+        Hgoto_error(1);
+    }
+    if (H5Pset_fapl_splitter(UC_opts.fapl_id, &split_fa) < 0) {
+        HDfprintf(stderr, "can't set creation FAPL\n");
+        H5Eprint2(H5E_DEFAULT, stdout);
+        Hgoto_error(1);
+    }
+
+    if (UC_opts.use_swmr) {
+        if (H5Pset_libver_bounds(UC_opts.fapl_id, H5F_LIBVER_LATEST, H5F_LIBVER_LATEST) < 0) {
+            HDfprintf(stderr, "can't set write FAPL libver bounds\n");
+            Hgoto_error(1);
+        }
+    }
+
+    if ((fid = H5Fopen(UC_opts.filename, H5F_ACC_RDWR | (UC_opts.use_swmr ? H5F_ACC_SWMR_WRITE : 0), UC_opts.fapl_id)) < 0) {
+        HDfprintf(stderr, "H5Fopen failed\n");
+        Hgoto_error(1);
+    }
+
+    if (write_uc_file(send_wait, fid, &UC_opts) < 0) {
+        HDfprintf(stderr, "write_uc_file encountered error\n");
+        Hgoto_error(1);
+    }
+
+    if (H5Fclose(fid) < 0) {
+        HDfprintf(stderr, "Failed to close write\n");
+        Hgoto_error(1);
+    }
+
+    if (H5Pclose(UC_opts.fapl_id) < 0) {
+        HDfprintf(stderr, "can't close write FAPL\n");
+        Hgoto_error(1);
+    }
+
+    if (H5Pclose(mirr_fapl_id) < 0) {
+        HDfprintf(stderr, "can't close write mirror FAPL\n");
+        Hgoto_error(1);
+    }
+
+    /* ================================================ */
+    /* If readwrite, collect exit code of child process */
+    /* ================================================ */
+    if (UC_opts.launch == UC_READWRITE) {
+        if ((tmppid = HDwaitpid(childpid, &child_status, child_wait_option)) < 0) {
+            HDperror("waitpid");
+            Hgoto_error(1);
+        }
+
+        if (WIFEXITED(child_status)) {
+            if ((child_ret_value = WEXITSTATUS(child_status)) != 0) {
+                HDprintf("%d: child process exited with non-zero code (%d)\n",
+                        mypid, child_ret_value);
+                Hgoto_error(2);
+            }
+        } else {
+            HDprintf("%d: child process terminated abnormally\n", mypid);
+            Hgoto_error(2);
+        }
+    }
+
+done:
+    if (ret_value != 0) {
+        HDprintf("Error(s) encountered\n");
+    } else {
+        HDprintf("All passed\n");
+    }
+
+    return(ret_value);
+}
+
+#else /* H5_HAVE_MIRROR_VFD */
+
+int
+main(void)
+{
+    HDfprintf(stderr, "Mirror VFD is not built. Skipping.\n");
+    return EXIT_SUCCESS;
+} /* end main() */
+
+#endif /* H5_HAVE_MIRROR_VFD */
+
+#else /* H5_HAVE_FORK */
+
+int
+main(void)
+{
+    HDfprintf(stderr, "Non-POSIX platform. Skipping.\n");
+    return EXIT_SUCCESS;
+} /* end main() */
+
+#endif /* H5_HAVE_FORK */
+
diff --git a/test/use_append_mchunks.c b/test/use_append_mchunks.c
index b7d45a4..2eb5a1d 100644
--- a/test/use_append_mchunks.c
+++ b/test/use_append_mchunks.c
@@ -29,14 +29,14 @@
  *     finishes HDF5 metadata updates and issues H5Fflush or H5Oflush calls.
  *   o Readers will see newly appended data after the Writer finishes
  *     the flush operation.
- * 
+ *
  * Preconditions:
  *   o Readers are not allowed to modify the file.
  *   o All datasets that are modified by the Writer exist when the
  *     Writer opens the file.
  *   o All datasets that are modified by the Writer exist when a Reader
  *     opens the file.
- * 
+ *
  * Main Success Scenario:
  *  1. An application creates a file with required objects (groups,
  *     datasets, and attributes).
@@ -45,7 +45,7 @@
  *     spans several chunks.
  *  3. A Reader opens the file and a dataset in a file; if the size of
  *     the unlimited dimension has changed, reads the appended data back.
- * 
+ *
  * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
 
 /* Created: Albert Cheng, 2013/6/1 */
@@ -61,46 +61,45 @@
 
 #include "use.h"
 
-/* Global Variable definitions */
-options_t UC_opts;	/* Use Case Options */
-const char *progname_g="use_append_mchunks";	/* program name */
+#define USE_APPEND_MCHUNKS_PROGNAME "use_append_mchunks"
+
+static options_t UC_opts; /* Use Case Options */
 
 /* Setup parameters for the use case.
  * Return: 0 succeed; -1 fail.
  */
-int setup_parameters(int argc, char * const argv[])
+int
+setup_parameters(int argc, char * const argv[], options_t * opts)
 {
     /* use case defaults */
-    HDmemset(&UC_opts, 0, sizeof(options_t));
-    UC_opts.chunksize = Chunksize_DFT;
-    UC_opts.use_swmr = 1;	/* use swmr open */
-    UC_opts.iterations = 1;
-    UC_opts.chunkplanes = 1;
-
-    /* parse options */
-    if (parse_option(argc, argv) < 0){
-	return(-1);
+    HDmemset(opts, 0, sizeof(options_t));
+    opts->chunksize = Chunksize_DFT;
+    opts->use_swmr = 1; /* use swmr open */
+    opts->iterations = 1;
+    opts->chunkplanes = 1;
+    opts->progname = USE_APPEND_MCHUNKS_PROGNAME;
+    opts->fapl_id = H5I_INVALID_HID;
+
+    if (parse_option(argc, argv, opts) < 0) {
+        return(-1);
     }
-    /* set chunk dims */
-    UC_opts.chunkdims[0] = (hsize_t)UC_opts.chunkplanes;
-    UC_opts.chunkdims[1] = UC_opts.chunkdims[2] = (hsize_t)UC_opts.chunksize;
 
-    /* set dataset initial and max dims */
-    UC_opts.dims[0] = 0;
-    UC_opts.max_dims[0] = H5S_UNLIMITED;
-    UC_opts.dims[1] = UC_opts.dims[2] = UC_opts.max_dims[1] = UC_opts.max_dims[2] = 2 * (hsize_t)UC_opts.chunksize;
+    opts->chunkdims[0] = (hsize_t)opts->chunkplanes;
+    opts->chunkdims[1] = opts->chunkdims[2] = (hsize_t)opts->chunksize;
+
+    opts->dims[0] = 0;
+    opts->max_dims[0] = H5S_UNLIMITED;
+    opts->dims[1] = opts->dims[2] = opts->max_dims[1] = opts->max_dims[2] = 2 * (hsize_t)opts->chunksize;
 
-    /* set nplanes */
-    if (UC_opts.nplanes == 0)
-        UC_opts.nplanes = 2 * (hsize_t)UC_opts.chunksize;
+    if (opts->nplanes == 0)
+        opts->nplanes = 2 * (hsize_t)opts->chunksize;
 
-    /* show parameters and return */
-    show_parameters();
+    show_parameters(opts);
     return(0);
-}
+} /* end setup_parameters() */
 
 
-/* Overall Algorithm: 
+/* Overall Algorithm:
  * Parse options from user;
  * Generate/pre-created test files needed and close it;
  * fork: child process becomes the reader process;
@@ -112,22 +111,20 @@ main(int argc, char *argv[])
 {
     pid_t childpid=0;
     pid_t mypid, tmppid;
-    int	child_status;
+    int child_status;
     int child_wait_option=0;
     int ret_value = 0;
     int child_ret_value;
     hbool_t send_wait = 0;
     hid_t fapl = -1;        /* File access property list */
     hid_t fid = -1;         /* File ID */
-    char *name;             /* Test file name */
 
-    /* initialization */
-    if (setup_parameters(argc, argv) < 0){
+    if (setup_parameters(argc, argv, &UC_opts) < 0) {
         Hgoto_error(1);
     }
 
     /* Determine the need to send/wait message file*/
-    if(UC_opts.launch == UC_READWRITE) {
+    if (UC_opts.launch == UC_READWRITE) {
         HDunlink(WRITER_MESSAGE);
         send_wait = 1;
     }
@@ -137,38 +134,63 @@ main(int argc, char *argv[])
     /* UC_WRITER:    create datafile, skip reader, launch writer.    */
     /* UC_READER:    skip create, launch reader, exit.               */
     /* ==============================================================*/
-    /* ============*/
+    /* =========== */
     /* Create file */
-    /* ============*/
-    if (UC_opts.launch != UC_READER){
+    /* =========== */
+    if (UC_opts.launch != UC_READER) {
         HDprintf("Creating skeleton data file for test...\n");
-	if (create_uc_file() < 0){
-	    HDfprintf(stderr, "***encounter error\n");
-	    Hgoto_error(1);
-	}else
-	    HDprintf("File created.\n");
+        if ((UC_opts.fapl_id = h5_fileaccess()) < 0) {
+            HDfprintf(stderr, "can't create creation FAPL\n");
+            Hgoto_error(1);
+        }
+        if (H5Pset_libver_bounds(UC_opts.fapl_id, H5F_LIBVER_LATEST, H5F_LIBVER_LATEST) < 0) {
+            HDfprintf(stderr, "can't set creation FAPL libver bounds\n");
+            Hgoto_error(1);
+        }
+        if (create_uc_file(&UC_opts) < 0) {
+            HDfprintf(stderr, "***encounter error\n");
+            Hgoto_error(1);
+        } else {
+            HDprintf("File created.\n");
+        }
+        /* Close FAPL to prevent issues with forking later */
+        if (H5Pclose(UC_opts.fapl_id) < 0) {
+            HDfprintf(stderr, "can't close creation FAPL\n");
+            Hgoto_error(1);
+        }
+        UC_opts.fapl_id = H5I_INVALID_HID;
     }
 
-    if (UC_opts.launch==UC_READWRITE){
-        /* fork process */
-        if((childpid = fork()) < 0) {
+    /* ============ */
+    /* Fork process */
+    /* ============ */
+    if (UC_opts.launch==UC_READWRITE) {
+        if ((childpid = fork()) < 0) {
             perror("fork");
             Hgoto_error(1);
-        };
-    };
+        }
+    }
     mypid = getpid();
 
     /* ============= */
     /* launch reader */
     /* ============= */
-    if (UC_opts.launch != UC_WRITER){
+    if (UC_opts.launch != UC_WRITER) {
         /* child process launch the reader */
-        if(0 == childpid) {
+        if (0 == childpid) {
             HDprintf("%d: launch reader process\n", mypid);
-            if (read_uc_file(send_wait) < 0){
+            if ((UC_opts.fapl_id = h5_fileaccess()) < 0) {
+                HDfprintf(stderr, "can't create read FAPL\n");
+                HDexit(EXIT_FAILURE);
+            }
+            if (read_uc_file(send_wait, &UC_opts) < 0) {
                 HDfprintf(stderr, "read_uc_file encountered error\n");
                 HDexit(EXIT_FAILURE);
             }
+            if (H5Pclose(UC_opts.fapl_id) < 0) {
+                HDfprintf(stderr, "can't close read FAPL\n");
+                HDexit(EXIT_FAILURE);
+            }
             HDexit(EXIT_SUCCESS);
         }
     }
@@ -179,51 +201,50 @@ main(int argc, char *argv[])
     /* this process continues to launch the writer */
     HDprintf("%d: continue as the writer process\n", mypid);
 
-    name = UC_opts.filename;
-
     /* Set the file access property list */
-    if((fapl = h5_fileaccess()) < 0)
+    if ((fapl = h5_fileaccess()) < 0) {
+        HDfprintf(stderr, "can't get write FAPL\n");
         Hgoto_error(1);
+    }
 
-    if(UC_opts.use_swmr)
-        if(H5Pset_libver_bounds(fapl, H5F_LIBVER_LATEST, H5F_LIBVER_LATEST) < 0)
+    if (UC_opts.use_swmr) {
+        if (H5Pset_libver_bounds(fapl, H5F_LIBVER_LATEST, H5F_LIBVER_LATEST) < 0) {
+            HDfprintf(stderr, "can't set write FAPL libver bounds\n");
             Hgoto_error(1);
+        }
+    }
 
-    /* Open the file */
-    if((fid = H5Fopen(name, H5F_ACC_RDWR | (UC_opts.use_swmr ? H5F_ACC_SWMR_WRITE : 0), fapl)) < 0) {
+    if ((fid = H5Fopen(UC_opts.filename, H5F_ACC_RDWR | (UC_opts.use_swmr ? H5F_ACC_SWMR_WRITE : 0), fapl)) < 0) {
         HDfprintf(stderr, "H5Fopen failed\n");
         Hgoto_error(1);
     }
 
-    if(write_uc_file(send_wait, fid) < 0) {
+    if (write_uc_file(send_wait, fid, &UC_opts) < 0) {
         HDfprintf(stderr, "write_uc_file encountered error\n");
         Hgoto_error(1);
     }
 
+    if (H5Fclose(fid) < 0) {
+        HDfprintf(stderr, "Failed to close file id\n");
+        Hgoto_error(1);
+    }
+
+    if (H5Pclose(fapl) < 0) {
+        HDfprintf(stderr, "can't close write FAPL\n");
+        Hgoto_error(1);
+    }
 
     /* ================================================ */
     /* If readwrite, collect exit code of child process */
     /* ================================================ */
-    if (UC_opts.launch == UC_READWRITE){
-        if ((tmppid = waitpid(childpid, &child_status, child_wait_option)) < 0){
+    if (UC_opts.launch == UC_READWRITE) {
+        if ((tmppid = waitpid(childpid, &child_status, child_wait_option)) < 0) {
             perror("waitpid");
             Hgoto_error(1);
         }
 
-        /* Close the file  */
-        if(H5Fclose(fid) < 0) {
-            HDfprintf(stderr, "Failed to close file id\n");
-            Hgoto_error(1);
-        }
-
-        /* Close the property list */
-        if(H5Pclose(fapl) < 0) {
-            HDfprintf(stderr, "Failed to close the property list\n");
-            Hgoto_error(1);
-        }
-
-        if (WIFEXITED(child_status)){
-            if ((child_ret_value=WEXITSTATUS(child_status)) != 0){
+        if (WIFEXITED(child_status)) {
+            if ((child_ret_value=WEXITSTATUS(child_status)) != 0) {
                 HDprintf("%d: child process exited with non-zero code (%d)\n",
                     mypid, child_ret_value);
                 Hgoto_error(1);
@@ -233,17 +254,16 @@ main(int argc, char *argv[])
             Hgoto_error(2);
         }
     }
-    
+
 done:
-    /* Print result and exit */
-    if (ret_value != 0){
+    if (ret_value != 0) {
         HDprintf("Error(s) encountered\n");
-    }else{
+    } else {
         HDprintf("All passed\n");
     }
 
     return(ret_value);
-}
+} /* end main() */
 
 #else /* H5_HAVE_FORK */
 
diff --git a/test/use_common.c b/test/use_common.c
index 4111b24..a986543 100644
--- a/test/use_common.c
+++ b/test/use_common.c
@@ -23,8 +23,13 @@
 
 #define H5D_FRIEND        /*suppress error about including H5Dpkg      */
 #define H5D_TESTING
-#include "H5Dpkg.h"
+#include "H5Dpkg.h" /* TODO : used to verify chunk index type (yes?) -- is there a way to do this sanity-check using the public API instead? */
 
+/* ----------------------------------------------------------------------------
+ * Print a common/shared usage message.
+ * Receives program name to show default test file name (<program_name>.h5).
+ * ----------------------------------------------------------------------------
+ */
 void
 usage(const char *prog)
 {
@@ -41,10 +46,13 @@ usage(const char *prog)
     HDfprintf(stderr, "\n");
 } /* end usage() */
 
-/* Setup Use Case parameters by parsing command line options.
-* Setup default values if not set by options. */
+/* ----------------------------------------------------------------------------
+ * Setup Use Case parameters by parsing command line options.
+ * Includes default values for unspecified options.
+ * ----------------------------------------------------------------------------
+ */
 int
-parse_option(int argc, char * const argv[])
+parse_option(int argc, char * const argv[], options_t * opts)
 {
     int ret_value=0;
     int c;
@@ -56,302 +64,307 @@ parse_option(int argc, char * const argv[])
     /* suppress getopt from printing error */
     opterr = 0;
 
-    while (1){
-    c = getopt (argc, argv, nagg_options);
-    if (-1 == c)
-        break;
-    switch (c) {
-    case 'h':
-        usage(progname_g);
-        HDexit(EXIT_SUCCESS);
-        break;
-    case 'f':    /* usecase data file name */
-        UC_opts.filename = optarg;
-        break;
-    case 'i':    /* iterations */
-        if ((UC_opts.iterations = HDatoi(optarg)) <= 0) {
-            HDfprintf(stderr, "bad iterations number %s, must be a positive integer\n", optarg);
-        usage(progname_g);
-        Hgoto_error(-1);
-        };
-        break;
-    case 'l':    /* launch reader or writer only */
-        switch (*optarg) {
-        case 'r':    /* reader only */
-        UC_opts.launch = UC_READER;
-        break;
-        case 'w': /* writer only */
-        UC_opts.launch = UC_WRITER;
-        break;
+    while (1) {
+        c = getopt(argc, argv, nagg_options);
+        if (-1 == c)
+            break;
+        switch (c) {
+        case 'h':
+            usage(opts->progname);
+            exit(EXIT_SUCCESS);
+            break;
+        case 'f':     /* usecase data file name */
+            opts->filename = optarg;
+            break;
+        case 'i':     /* iterations */
+            if ((opts->iterations = HDatoi(optarg)) <= 0) {
+                HDfprintf(stderr, "bad iterations number %s, must be a positive integer\n", optarg);
+                usage(opts->progname);
+                Hgoto_error(-1);
+            }
+            break;
+        case 'l':     /* launch reader or writer only */
+            switch (*optarg) {
+            case 'r': /* reader only */
+                opts->launch = UC_READER;
+                break;
+            case 'w': /* writer only */
+                opts->launch = UC_WRITER;
+                break;
+            default:
+                HDfprintf(stderr, "launch value(%c) should be w or r only.\n", *optarg);
+                usage(opts->progname);
+                Hgoto_error(-1);
+                break;
+            } /* end switch (reader/writer-only mode toggle) */
+            break;
+        case 'n':     /* number of planes to write/read */
+            if ((opts->nplanes = HDstrtoul(optarg, NULL, 0)) <= 0) {
+                HDfprintf(stderr, "bad number of planes %s, must be a positive integer\n", optarg);
+                usage(opts->progname);
+                Hgoto_error(-1);
+            }
+            break;
+        case 's':     /* use swmr file open mode */
+            use_swmr = HDatoi(optarg);
+            if (use_swmr != 0 && use_swmr != 1) {
+                HDfprintf(stderr, "swmr value should be 0(no) or 1(yes)\n");
+                usage(opts->progname);
+                Hgoto_error(-1);
+            }
+            opts->use_swmr = (hbool_t)use_swmr;
+            break;
+        case 'y':     /* Number of planes per chunk */
+            if ((opts->chunkplanes = HDstrtoul(optarg, NULL, 0)) <= 0) {
+                HDfprintf(stderr, "bad number of planes per chunk %s, must be a positive integer\n", optarg);
+                usage(opts->progname);
+                Hgoto_error(-1);
+            }
+            break;
+        case 'z':     /* size of chunk=(z,z) */
+            if ((opts->chunksize = HDstrtoull(optarg, NULL, 0)) <= 0) {
+                HDfprintf(stderr, "bad chunksize %s, must be a positive integer\n", optarg);
+                usage(opts->progname);
+                Hgoto_error(-1);
+            }
+            break;
+        case '?':
+            HDfprintf(stderr, "getopt returned '%c'.\n", c);
+            Hgoto_error(-1);
         default:
-            HDfprintf(stderr, "launch value(%c) should be w or r only.\n", *optarg);
-        usage(progname_g);
-        Hgoto_error(-1);
-        break;
-        }
-        break;
-    case 'n':    /* number of planes to write/read */
-        if ((UC_opts.nplanes = HDstrtoul(optarg, NULL, 0)) <= 0) {
-            HDfprintf(stderr, "bad number of planes %s, must be a positive integer\n", optarg);
-        usage(progname_g);
-        Hgoto_error(-1);
-        };
-        break;
-    case 's':    /* use swmr file open mode */
-        use_swmr = HDatoi(optarg);
-        if (use_swmr != 0 && use_swmr != 1) {
-            HDfprintf(stderr, "swmr value should be 0(no) or 1(yes)\n");
-            usage(progname_g);
+            HDfprintf(stderr, "getopt returned unexpected value.\n");
+            HDfprintf(stderr, "Unexpected value is %d\n", c);
             Hgoto_error(-1);
-        }
-        UC_opts.use_swmr = (hbool_t)use_swmr;
-        break;
-    case 'y':    /* Number of planes per chunk */
-        if ((UC_opts.chunkplanes = HDstrtoul(optarg, NULL, 0)) <= 0) {
-            HDfprintf(stderr, "bad number of planes per chunk %s, must be a positive integer\n", optarg);
-        usage(progname_g);
-        Hgoto_error(-1);
-        };
-        break;
-    case 'z':    /* size of chunk=(z,z) */
-        if ((UC_opts.chunksize = HDstrtoull(optarg, NULL, 0)) <= 0) {
-            HDfprintf(stderr, "bad chunksize %s, must be a positive integer\n", optarg);
-        usage(progname_g);
-        Hgoto_error(-1);
-        };
-        break;
-    case '?':
-        HDfprintf(stderr, "getopt returned '%c'.\n", c);
-        Hgoto_error(-1);
-    default:
-        HDfprintf(stderr, "getopt returned unexpected value.\n");
-        HDfprintf(stderr, "Unexpected value is %d\n", c);
-        Hgoto_error(-1);
-    }
-    }
+        } /* end switch (argument symbol) */
+    } /* end while (there are still arguments) */
 
     /* set test file name if not given */
-    if (!UC_opts.filename){
-    /* default data file name is <progname>.h5 */
-    if ((UC_opts.filename=(char*)HDmalloc(HDstrlen(progname_g)+4))==NULL) {
-        HDfprintf(stderr, "malloc: failed\n");
-        Hgoto_error(-1);
-    };
-    HDstrcpy(UC_opts.filename, progname_g);
-    HDstrcat(UC_opts.filename, ".h5");
+    if (!opts->filename) {
+        /* default data file name is <progname>.h5 */
+        if ((opts->filename=(char*)HDmalloc(HDstrlen(opts->progname)+4))==NULL) {
+            HDfprintf(stderr, "malloc: failed\n");
+            Hgoto_error(-1);
+        }
+        HDstrcpy(opts->filename, opts->progname);
+        HDstrcat(opts->filename, ".h5");
     }
 
 done:
-    /* All done. */
     return(ret_value);
-}
+} /* end parse_option() */
 
-/* Show parameters used for this use case */
-void show_parameters(void){
+/* ----------------------------------------------------------------------------
+ * Show parameters used for this use case.
+ * ----------------------------------------------------------------------------
+ */
+void
+show_parameters(options_t * opts)
+{
     HDprintf("===Parameters used:===\n");
-    printf("chunk dims=(%llu, %llu, %llu)\n", (unsigned long long)UC_opts.chunkdims[0],
-        (unsigned long long)UC_opts.chunkdims[1], (unsigned long long)UC_opts.chunkdims[2]);
-    printf("dataset max dims=(%llu, %llu, %llu)\n", (unsigned long long)UC_opts.max_dims[0],
-        (unsigned long long)UC_opts.max_dims[1], (unsigned long long)UC_opts.max_dims[2]);
-    HDprintf("number of planes to write=%llu\n", (unsigned long long)UC_opts.nplanes);
-    HDprintf("using SWMR mode=%s\n", UC_opts.use_swmr ? "yes(1)" : "no(0)");
-    HDprintf("data filename=%s\n", UC_opts.filename);
+    HDprintf("chunk dims=(%llu, %llu, %llu)\n", (unsigned long long)opts->chunkdims[0], 
+        (unsigned long long)opts->chunkdims[1], (unsigned long long)opts->chunkdims[2]);
+    HDprintf("dataset max dims=(%llu, %llu, %llu)\n", (unsigned long long)opts->max_dims[0], 
+        (unsigned long long)opts->max_dims[1], (unsigned long long)opts->max_dims[2]);
+    HDprintf("number of planes to write=%llu\n", (unsigned long long)opts->nplanes);
+    HDprintf("using SWMR mode=%s\n", opts->use_swmr ? "yes(1)" : "no(0)");
+    HDprintf("data filename=%s\n", opts->filename);
     HDprintf("launch part=");
-    switch (UC_opts.launch){
-    case UC_READWRITE:
-        printf("Reader/Writer\n");
-        break;
-    case UC_WRITER:
-        printf("Writer\n");
-        break;
-    case UC_READER:
-        printf("Reader\n");
-        break;
-    default:
-        /* should not happen */
-        printf("Illegal part(%d)\n", UC_opts.launch);
-    };
-    HDprintf("number of iterations=%d (not used yet)\n", UC_opts.iterations);
+        switch (opts->launch) {
+        case UC_READWRITE:
+            HDprintf("Reader/Writer\n");
+            break;
+        case UC_WRITER:
+            HDprintf("Writer\n");
+            break;
+        case UC_READER:
+            HDprintf("Reader\n");
+            break;
+        default:
+            /* should not happen */
+            HDprintf("Illegal part(%d)\n", opts->launch);
+        }
+    HDprintf("number of iterations=%d (not used yet)\n", opts->iterations);
     HDprintf("===Parameters shown===\n");
-}
+} /* end show_parameters() */
 
-/* Create the skeleton use case file for testing.
+/* ----------------------------------------------------------------------------
+ * Create the skeleton use case file for testing.
  * It has one 3d dataset using chunked storage.
  * The dataset is (unlimited, chunksize, chunksize).
  * Dataset type is 2 bytes integer.
  * It starts out "empty", i.e., first dimension is 0.
  *
  * Return: 0 succeed; -1 fail.
+ * ----------------------------------------------------------------------------
  */
-int create_uc_file(void)
+int
+create_uc_file(options_t * opts)
 {
-    hsize_t dims[3];        /* Dataset starting dimensions */
-    hid_t fid;          /* File ID for new HDF5 file */
-    hid_t dcpl;         /* Dataset creation property list */
-    hid_t sid;          /* Dataspace ID */
-    hid_t dsid;         /* Dataset ID */
-    hid_t fapl;         /* File access property list */
+    hsize_t dims[3];            /* Dataset starting dimensions */
+    hid_t fid;                  /* File ID for new HDF5 file */
+    hid_t dcpl;                 /* Dataset creation property list */
+    hid_t sid;                  /* Dataspace ID */
+    hid_t dsid;                 /* Dataset ID */
     H5D_chunk_index_t idx_type; /* Chunk index type */
 
-    /* Create the file */
-    if((fapl = h5_fileaccess()) < 0)
-        return -1;
-    if(H5Pset_libver_bounds(fapl, H5F_LIBVER_LATEST, H5F_LIBVER_LATEST) < 0)
-        return -1;
-    if((fid = H5Fcreate(UC_opts.filename, H5F_ACC_TRUNC, H5P_DEFAULT, fapl)) < 0)
+    if ((fid = H5Fcreate(opts->filename, H5F_ACC_TRUNC, H5P_DEFAULT, opts->fapl_id)) < 0)
         return -1;
 
     /* Set up dimension sizes */
     dims[0] = 0;
-    dims[1] = dims[2] = UC_opts.max_dims[1];
+    dims[1] = dims[2] = opts->max_dims[1];
 
     /* Create dataspace for creating datasets */
-    if((sid = H5Screate_simple(3, dims, UC_opts.max_dims)) < 0)
+    if ((sid = H5Screate_simple(3, dims, opts->max_dims)) < 0)
         return -1;
 
     /* Create dataset creation property list */
-    if((dcpl = H5Pcreate(H5P_DATASET_CREATE)) < 0)
+    if ((dcpl = H5Pcreate(H5P_DATASET_CREATE)) < 0)
         return -1;
-    if(H5Pset_chunk(dcpl, 3, UC_opts.chunkdims) < 0)
+    if (H5Pset_chunk(dcpl, 3, opts->chunkdims) < 0)
         return -1;
 
     /* create dataset of progname */
-    if((dsid = H5Dcreate2(fid, progname_g, UC_DATATYPE, sid, H5P_DEFAULT, dcpl, H5P_DEFAULT)) < 0)
-    return -1;
+    if ((dsid = H5Dcreate2(fid, opts->progname, UC_DATATYPE, sid, H5P_DEFAULT, dcpl, H5P_DEFAULT)) < 0)
+        return -1;
 
     /* Check that the chunk index type is not version 1 B-tree.
      * Version 1 B-trees are not supported under SWMR.
      */
-    if(H5D__layout_idx_type_test(dsid, &idx_type) < 0)
+    if (H5D__layout_idx_type_test(dsid, &idx_type) < 0)
         return -1;
-    if(idx_type == H5D_CHUNK_IDX_BTREE) {
+    if (idx_type == H5D_CHUNK_IDX_BTREE) {
         HDfprintf(stderr, "ERROR: Chunk index is version 1 B-tree: aborting.\n");
         return -1;
     }
 
     /* Close everything */
-    if(H5Dclose(dsid) < 0)
-    return -1;
-    if(H5Pclose(fapl) < 0)
+    if (H5Dclose(dsid) < 0)
         return -1;
-    if(H5Pclose(dcpl) < 0)
+    if (H5Pclose(dcpl) < 0)
         return -1;
-    if(H5Sclose(sid) < 0)
+    if (H5Sclose(sid) < 0)
         return -1;
-    if(H5Fclose(fid) < 0)
+    if (H5Fclose(fid) < 0)
         return -1;
 
     return 0;
-}
+} /* end create_uc_file() */
 
-/* Append planes, each of (1,2*chunksize,2*chunksize) to the dataset.
+/* ----------------------------------------------------------------------------
+ * Append planes, each of (1,2*chunksize,2*chunksize) to the dataset.
  * In other words, 4 chunks are appended to the dataset at a time.
  * Fill each plan with the plane number and then write it at the nth plane.
  * Increase the plane number and repeat till the end of dataset, when it
  * reaches chunksize long. End product is a (2*chunksize)^3 cube.
  *
  * Return: 0 succeed; -1 fail.
+ * ----------------------------------------------------------------------------
  */
-int write_uc_file(hbool_t tosend, hid_t fid)
+int
+write_uc_file(hbool_t tosend, hid_t file_id, options_t * opts)
 {
-    hid_t    dsid;         /* dataset ID */
-    hid_t    dcpl;         /* Dataset creation property list */
-    UC_CTYPE    *buffer, *bufptr;    /* data buffer */
-    hsize_t    cz=UC_opts.chunksize;        /* Chunk size */
-    hid_t    f_sid;        /* dataset file space id */
-    hid_t    m_sid;        /* memory space id */
-    int        rank;        /* rank */
-    hsize_t     chunk_dims[3];    /* Chunk dimensions */
-    hsize_t    dims[3];    /* Dataspace dimensions */
-    hsize_t    memdims[3]; /* Memory space dimensions */
-    hsize_t    start[3] = {0,0,0}, count[3];    /* Hyperslab selection values */
-    hsize_t     i, j, k;
-
-    if(tosend)
+    hid_t     dsid;                         /* dataset ID */
+    hid_t     dcpl;                         /* Dataset creation property list */
+    UC_CTYPE *buffer, *bufptr;              /* data buffer */
+    hsize_t   cz=opts->chunksize;           /* Chunk size */
+    hid_t     f_sid;                        /* dataset file space id */
+    hid_t     m_sid;                        /* memory space id */
+    int       rank;                         /* rank */
+    hsize_t   chunk_dims[3];                /* Chunk dimensions */
+    hsize_t   dims[3];                      /* Dataspace dimensions */
+    hsize_t   memdims[3];                   /* Memory space dimensions */
+    hsize_t   start[3] = {0,0,0}, count[3]; /* Hyperslab selection values */
+    hsize_t   i, j, k;
+
+    if (TRUE == tosend) {
         /* Send a message that H5Fopen is complete--releasing the file lock */
         h5_send_message(WRITER_MESSAGE, NULL, NULL);
+    }
 
     /* Open the dataset of the program name */
-    if((dsid = H5Dopen2(fid, progname_g, H5P_DEFAULT)) < 0){
+    if ((dsid = H5Dopen2(file_id, opts->progname, H5P_DEFAULT)) < 0) {
         HDfprintf(stderr, "H5Dopen2 failed\n");
         return -1;
     }
 
     /* Find chunksize used */
-    if ((dcpl = H5Dget_create_plist(dsid)) < 0){
+    if ((dcpl = H5Dget_create_plist(dsid)) < 0) {
         HDfprintf(stderr, "H5Dget_create_plist failed\n");
         return -1;
     }
-    if (H5D_CHUNKED != H5Pget_layout(dcpl)){
+    if (H5D_CHUNKED != H5Pget_layout(dcpl)) {
         HDfprintf(stderr, "storage layout is not chunked\n");
         return -1;
     }
-    if ((rank = H5Pget_chunk(dcpl, 3, chunk_dims)) != 3){
+    if ((rank = H5Pget_chunk(dcpl, 3, chunk_dims)) != 3) {
         HDfprintf(stderr, "storage rank is not 3\n");
         return -1;
     }
 
     /* verify chunk_dims against set paramenters */
-    if (chunk_dims[0]!=UC_opts.chunkdims[0] || chunk_dims[1] != cz || chunk_dims[2] != cz){
+    if (chunk_dims[0]!=opts->chunkdims[0] || chunk_dims[1] != cz || chunk_dims[2] != cz) {
         HDfprintf(stderr, "chunk size is not as expected. Got dims=(%llu,%llu,%llu)\n",
-        (unsigned long long)chunk_dims[0], (unsigned long long)chunk_dims[1],
+            (unsigned long long)chunk_dims[0], (unsigned long long)chunk_dims[1], 
             (unsigned long long)chunk_dims[2]);
         return -1;
     }
 
     /* allocate space for data buffer 1 X dims[1] X dims[2] of UC_CTYPE */
     memdims[0]=1;
-    memdims[1] = UC_opts.dims[1];
-    memdims[2] = UC_opts.dims[2];
+    memdims[1] = opts->dims[1];
+    memdims[2] = opts->dims[2];
     if ((buffer=(UC_CTYPE*)HDmalloc((size_t)memdims[1]*(size_t)memdims[2]*sizeof(UC_CTYPE)))==NULL) {
         HDfprintf(stderr, "malloc: failed\n");
         return -1;
-    };
+    }
 
     /*
      * Get dataset rank and dimension.
      */
     f_sid = H5Dget_space(dsid);    /* Get filespace handle first. */
     rank  = H5Sget_simple_extent_ndims(f_sid);
-    if (rank != UC_RANK){
+    if (rank != UC_RANK) {
         HDfprintf(stderr, "rank(%d) of dataset does not match\n", rank);
         return -1;
     }
-    if (H5Sget_simple_extent_dims(f_sid, dims, NULL) < 0){
+    if (H5Sget_simple_extent_dims(f_sid, dims, NULL) < 0) {
         HDfprintf(stderr, "H5Sget_simple_extent_dims got error\n");
         return -1;
     }
     HDprintf("dataset rank %d, dimensions %llu x %llu x %llu\n",
-    rank, (unsigned long long)(dims[0]), (unsigned long long)(dims[1]),
+           rank, (unsigned long long)(dims[0]), (unsigned long long)(dims[1]), 
            (unsigned long long)(dims[2]));
     /* verify that file space dims are as expected and are consistent with memory space dims */
-    if (dims[0] != 0 || dims[1] != memdims[1] || dims[2] != memdims[2]){
+    if (dims[0] != 0 || dims[1] != memdims[1] || dims[2] != memdims[2]) {
         HDfprintf(stderr, "dataset is not empty. Got dims=(%llu,%llu,%llu)\n",
-        (unsigned long long)dims[0], (unsigned long long)dims[1],
+            (unsigned long long)dims[0], (unsigned long long)dims[1], 
             (unsigned long long)dims[2]);
         return -1;
     }
 
     /* setup mem-space for buffer */
-    if ((m_sid=H5Screate_simple(rank, memdims, NULL))<0){
+    if ((m_sid=H5Screate_simple(rank, memdims, NULL))<0) {
         HDfprintf(stderr, "H5Screate_simple for memory failed\n");
         return -1;
-    };
+    }
 
     /* write planes */
     count[0]=1;
     count[1]=dims[1];
     count[2]=dims[2];
-    for (i=0; i<UC_opts.nplanes; i++){
+    for (i=0; i < opts->nplanes; i++) {
         /* fill buffer with value i+1 */
         bufptr = buffer;
-        for (j=0; j<dims[1]; j++)
-            for (k=0; k<dims[2]; k++)
+        for (j=0; j < dims[1]; j++) {
+            for (k=0; k < dims[2]; k++) {
                 *bufptr++ = (UC_CTYPE)i;
+            }
+        }
 
         /* Cork the dataset's metadata in the cache, if SWMR is enabled */
-        if(UC_opts.use_swmr) {
-            if(H5Odisable_mdc_flushes(dsid) < 0) {
+        if (opts->use_swmr) {
+            if (H5Odisable_mdc_flushes(dsid) < 0) {
                 HDfprintf(stderr, "H5Odisable_mdc_flushes failed\n");
                 return -1;
             }
@@ -359,64 +372,65 @@ int write_uc_file(hbool_t tosend, hid_t fid)
 
         /* extend the dataset by one for new plane */
         dims[0]=i+1;
-        if(H5Dset_extent(dsid, dims) < 0){
+        if (H5Dset_extent(dsid, dims) < 0) {
             HDfprintf(stderr, "H5Dset_extent failed\n");
             return -1;
         }
 
         /* Get the dataset's dataspace */
-        if((f_sid = H5Dget_space(dsid)) < 0){
+        if ((f_sid = H5Dget_space(dsid)) < 0) {
             HDfprintf(stderr, "H5Dset_extent failed\n");
             return -1;
         }
 
         start[0]=i;
         /* Choose the next plane to write */
-        if(H5Sselect_hyperslab(f_sid, H5S_SELECT_SET, start, NULL, count, NULL) < 0){
+        if (H5Sselect_hyperslab(f_sid, H5S_SELECT_SET, start, NULL, count, NULL) < 0) {
             HDfprintf(stderr, "Failed H5Sselect_hyperslab\n");
             return -1;
         }
 
         /* Write plane to the dataset */
-        if(H5Dwrite(dsid, UC_DATATYPE, m_sid, f_sid, H5P_DEFAULT, buffer) < 0){
+        if (H5Dwrite(dsid, UC_DATATYPE, m_sid, f_sid, H5P_DEFAULT, buffer) < 0) {
             HDfprintf(stderr, "Failed H5Dwrite\n");
             return -1;
         }
 
         /* Uncork the dataset's metadata from the cache, if SWMR is enabled */
-        if(UC_opts.use_swmr)
-            if(H5Oenable_mdc_flushes(dsid) < 0) {
+        if (opts->use_swmr) {
+            if (H5Oenable_mdc_flushes(dsid) < 0) {
                 HDfprintf(stderr, "H5Oenable_mdc_flushes failed\n");
                 return -1;
             }
+        }
 
         /* flush file to make the just written plane available. */
-        if(H5Dflush(dsid) < 0) {
+        if (H5Dflush(dsid) < 0) {
             HDfprintf(stderr, "Failed to H5Fflush file\n");
             return -1;
         }
-    }
+    } /* end for each plane to write */
 
     /* Done writing. Free/Close all resources including data file */
     HDfree(buffer);
-    if (H5Dclose(dsid) < 0){
+    if (H5Dclose(dsid) < 0) {
         HDfprintf(stderr, "Failed to close datasete\n");
         return -1;
     }
-    if (H5Sclose(m_sid) < 0){
+    if (H5Sclose(m_sid) < 0) {
         HDfprintf(stderr, "Failed to close memory space\n");
         return -1;
     }
-    if (H5Sclose(f_sid) < 0){
+    if (H5Sclose(f_sid) < 0) {
         HDfprintf(stderr, "Failed to close file space\n");
         return -1;
     }
 
     return 0;
-}
-
+} /* end write_uc_file() */
 
-/* Read planes from the dataset.
+/* ----------------------------------------------------------------------------
+ * Read planes from the dataset.
  * It expects the dataset is being changed (growing).
  * It checks the unlimited dimension (1st one). When it increases,
  * it will read in the new planes, one by one, and verify the data correctness.
@@ -425,61 +439,51 @@ int write_uc_file(hbool_t tosend, hid_t fid)
  * that is the expected end of data, the reader exits.
  *
  * Return: 0 succeed; -1 fail.
+ * ----------------------------------------------------------------------------
  */
-int read_uc_file(hbool_t towait)
+int
+read_uc_file(hbool_t towait, options_t * opts)
 {
-    hid_t   fapl;         /* file access property list ID */
-    hid_t    fid;          /* File ID for new HDF5 file */
-    hid_t    dsid;         /* dataset ID */
-    char    *name;
-    UC_CTYPE    *buffer, *bufptr;    /* read data buffer */
-    hid_t    f_sid;        /* dataset file space id */
-    hid_t    m_sid;        /* memory space id */
-    int        rank;        /* rank */
-    hsize_t    dims[3];    /* Dataspace dimensions */
-    hsize_t    memdims[3]; /* Memory space dimensions */
-    hsize_t     nplane=0, nplane_old=0;    /* nth plane, last nth plane */
-    hsize_t    start[3] = {0,0,0}, count[3];    /* Hyperslab selection values */
-    hsize_t    j, k;
-    int        nreadererr=0;
-    int        nerrs;
-    int        nonewplane;
+    hid_t     fid;                          /* File ID for new HDF5 file */
+    hid_t     dsid;                         /* dataset ID */
+    UC_CTYPE *buffer, *bufptr;              /* read data buffer */
+    hid_t     f_sid;                        /* dataset file space id */
+    hid_t     m_sid;                        /* memory space id */
+    int       rank;                         /* rank */
+    hsize_t   dims[3];                      /* Dataspace dimensions */
+    hsize_t   memdims[3];                   /* Memory space dimensions */
+    hsize_t   nplane=0, nplanes_seen=0;     /* nth plane, last nth plane */
+    hsize_t   start[3] = {0,0,0}, count[3]; /* Hyperslab selection values */
+    hsize_t   j, k;
+    int       nreadererr=0;
+    int       nerrs;
+    int       loops_waiting_for_plane;
 
     /* Before reading, wait for the message that H5Fopen is complete--file lock is released */
-    if(towait && h5_wait_message(WRITER_MESSAGE) < 0) {
+    if (towait && h5_wait_message(WRITER_MESSAGE) < 0) {
         HDfprintf(stderr, "Cannot find writer message file...failed\n");
         return -1;
     }
 
-    name = UC_opts.filename;
-
-    /* Open the file */
-    if((fapl = h5_fileaccess()) < 0)
-        return -1;
-    if((fid = H5Fopen(name, H5F_ACC_RDONLY | (UC_opts.use_swmr ? H5F_ACC_SWMR_READ : 0), fapl)) < 0){
+    HDfprintf(stderr, "Opening to read %s\n", opts->filename);
+    if ((fid = H5Fopen(opts->filename, H5F_ACC_RDONLY | (opts->use_swmr ? H5F_ACC_SWMR_READ : 0), opts->fapl_id)) < 0) {
         HDfprintf(stderr, "H5Fopen failed\n");
         return -1;
     }
-    if (H5Pclose(fapl) < 0){
-        HDfprintf(stderr, "Failed to property list\n");
-        return -1;
-    }
-
 
-    /* Open the dataset of the program name */
-    if((dsid = H5Dopen2(fid, progname_g, H5P_DEFAULT)) < 0){
+    if ((dsid = H5Dopen2(fid, opts->progname, H5P_DEFAULT)) < 0) {
         HDfprintf(stderr, "H5Dopen2 failed\n");
         return -1;
     }
 
-    /* allocate space for data buffer 1 X dims[1] X dims[2] of UC_CTYPE */
-    memdims[0]=1;
-    memdims[1] = UC_opts.dims[1];
-    memdims[2] = UC_opts.dims[2];
+    /* Allocate space for data buffer 1 X dims[1] X dims[2] of UC_CTYPE */
+    memdims[0] = 1;
+    memdims[1] = opts->dims[1];
+    memdims[2] = opts->dims[2];
     if ((buffer=(UC_CTYPE*)HDmalloc((size_t)memdims[1]*(size_t)memdims[2]*sizeof(UC_CTYPE)))==NULL) {
         HDfprintf(stderr, "malloc: failed\n");
         return -1;
-    };
+    }
 
     /*
      * Get dataset rank and dimension.
@@ -487,11 +491,11 @@ int read_uc_file(hbool_t towait)
      */
     f_sid = H5Dget_space(dsid);    /* Get filespace handle first. */
     rank  = H5Sget_simple_extent_ndims(f_sid);
-    if (rank != UC_RANK){
+    if (rank != UC_RANK) {
         HDfprintf(stderr, "rank(%d) of dataset does not match\n", rank);
         return -1;
     }
-    if (H5Sget_simple_extent_dims(f_sid, dims, NULL) < 0){
+    if (H5Sget_simple_extent_dims(f_sid, dims, NULL) < 0) {
         HDfprintf(stderr, "H5Sget_simple_extent_dims got error\n");
         return -1;
     }
@@ -499,7 +503,7 @@ int read_uc_file(hbool_t towait)
             rank, (unsigned long long)(dims[0]), (unsigned long long)(dims[1]),
             (unsigned long long)(dims[2]));
     /* verify that file space dims are as expected and are consistent with memory space dims */
-    if (dims[1] != memdims[1] || dims[2] != memdims[2]){
+    if (dims[1] != memdims[1] || dims[2] != memdims[2]) {
         HDfprintf(stderr, "dataset dimension is not as expected. Got dims=(%llu,%llu,%llu)\n",
             (unsigned long long)dims[0], (unsigned long long)dims[1],
             (unsigned long long)dims[2]);
@@ -509,120 +513,101 @@ int read_uc_file(hbool_t towait)
         return -1;
     }
 
-    /* setup mem-space for buffer */
-    if ((m_sid=H5Screate_simple(rank, memdims, NULL))<0){
+    /* Setup mem-space for buffer */
+    if ((m_sid=H5Screate_simple(rank, memdims, NULL)) < 0) {
         HDfprintf(stderr, "H5Screate_simple for memory failed\n");
         return -1;
-    };
+    }
 
-    /* Read 1 plane at a time whenever the dataset grows larger
-     * (along dim[0]) */
-    count[0]=1;
-    count[1]=dims[1];
-    count[2]=dims[2];
+    /* Read 1 plane at a time whenever the dataset grows larger (along dim[0]) */
+    count[0] = 1;
+    count[1] = dims[1];
+    count[2] = dims[2];
     /* quit when all nplanes  have been read */
-    nonewplane=0;
-    while (nplane_old < UC_opts.nplanes ){
-    /* print progress message according to if new planes are availalbe */
-    if (nplane_old < dims[0]) {
-        if (nonewplane){
-            /* end the previous message */
-            HDprintf("\n");
-            nonewplane=0;
-        }
-        HDprintf("reading planes %llu to %llu\n", (unsigned long long)nplane_old,
+    loops_waiting_for_plane=0;
+    while (nplanes_seen < opts->nplanes) {
+        /* print progress message according to if new planes are availalbe */
+        if (nplanes_seen < dims[0]) {
+            if (loops_waiting_for_plane) {
+                /* end the previous message */
+                HDprintf("\n");
+                loops_waiting_for_plane=0;
+            }
+            HDprintf("reading planes %llu to %llu\n", (unsigned long long)nplanes_seen, 
                 (unsigned long long)dims[0]);
-    }else{
-        if (nonewplane){
-            HDprintf(".");
-        if (nonewplane>=30){
-            HDfprintf(stderr, "waited too long for new plane, quit.\n");
-            return -1;
-        }
-        }else{
-            /* print mesg only the first time; dots still no new plane */
-            HDprintf("no new planes to read ");
         }
-        nonewplane++;
-        /* pause for a second */
-        HDsleep(1);
-    }
-    for (nplane=nplane_old; nplane < dims[0]; nplane++){
-        /* read planes between last old nplanes and current extent */
-        /* Get the dataset's dataspace */
-        if((f_sid = H5Dget_space(dsid)) < 0){
-            HDfprintf(stderr, "H5Dget_space failed\n");
-            return -1;
+        else {
+            if (loops_waiting_for_plane) {
+                HDprintf(".");
+                if (loops_waiting_for_plane>=30) {
+                    HDfprintf(stderr, "waited too long for new plane, quit.\n");
+                    return -1;
+                }
+            }
+            else {
+                /* print mesg only the first time; dots still no new plane */
+                HDprintf("waiting for new planes to read ");
+            }
+            loops_waiting_for_plane++;
+            /* pause for a second */
+            HDsleep(1);
         }
 
-        start[0]=nplane;
-        /* Choose the next plane to read */
-        if(H5Sselect_hyperslab(f_sid, H5S_SELECT_SET, start, NULL, count, NULL) < 0){
-            HDfprintf(stderr, "H5Sselect_hyperslab failed\n");
-            return -1;
-        }
+        for (nplane=nplanes_seen; nplane < dims[0]; nplane++) {
+            /* read planes between last old nplanes and current extent */
+            /* Get the dataset's dataspace */
+            if ((f_sid = H5Dget_space(dsid)) < 0) {
+                HDfprintf(stderr, "H5Dget_space failed\n");
+                return -1;
+            }
 
-        /* Read the plane from the dataset */
-        if(H5Dread(dsid, UC_DATATYPE, m_sid, f_sid, H5P_DEFAULT, buffer) < 0){
-            HDfprintf(stderr, "H5Dread failed\n");
-            return -1;
-        }
+            start[0]=nplane;
+            /* Choose the next plane to read */
+            if (H5Sselect_hyperslab(f_sid, H5S_SELECT_SET, start, NULL, count, NULL) < 0) {
+                HDfprintf(stderr, "H5Sselect_hyperslab failed\n");
+                return -1;
+            }
 
-        /* compare read data with expected data value which is nplane */
-        bufptr = buffer;
-        nerrs=0;
-        for (j=0; j<dims[1]; j++){
-            for (k=0; k<dims[2]; k++){
-                if ((hsize_t)*bufptr++ != nplane){
-                    if (++nerrs < ErrorReportMax){
-                        HDfprintf(stderr,
-                            "found error %llu plane(%llu,%llu), expected %llu, got %d\n",
-                            (unsigned long long)nplane, (unsigned long long)j,
-                            (unsigned long long)k, (unsigned long long)nplane, (int)*(bufptr-1));
-                    }
-                }
+            /* Read the plane from the dataset */
+            if (H5Dread(dsid, UC_DATATYPE, m_sid, f_sid, H5P_DEFAULT, buffer) < 0) {
+                HDfprintf(stderr, "H5Dread failed\n");
+                return -1;
             }
-        }
-        if (nerrs){
-            nreadererr++;
-            HDfprintf(stderr, "found %d unexpected values in plane %llu\n", nerrs,
+
+            /* compare read data with expected data value which is nplane */
+            bufptr = buffer;
+            nerrs=0;
+            for (j=0; j < dims[1]; j++) {
+                for (k=0; k < dims[2]; k++) {
+                    if ((hsize_t)*bufptr++ != nplane) {
+                        if (++nerrs < ErrorReportMax) {
+                            HDfprintf(stderr,
+                                "found error %llu plane(%llu,%llu), expected %llu, got %d\n",
+                                (unsigned long long)nplane, (unsigned long long)j, 
+                                (unsigned long long)k, (unsigned long long)nplane, (int)*(bufptr-1));
+                        } /* end if should print error */
+                    } /* end if value mismatch */
+                } /* end for plane second dimension */
+            } /* end for plane first dimension */
+            if (nerrs) {
+                nreadererr++;
+                HDfprintf(stderr, "found %d unexpected values in plane %llu\n", nerrs, 
                     (unsigned long long)nplane);
-        }
-    }
-    /* Have read all current planes */
-    nplane_old=dims[0];
+            }
+        } /* end for each plane added since last read */
 
-    /* check if dataset has grown since last time */
-#if 0
-    /* close dsid and file, then reopen them */
-    if (H5Dclose(dsid) < 0){
-        HDfprintf(stderr, "H5Dclose failed\n");
-        return -1;
-    }
-    if (H5Fclose(fid) < 0){
-        HDfprintf(stderr, "H5Fclose failed\n");
-        return -1;
-    }
-    if((fid = H5Fopen(name, H5F_ACC_RDONLY | (UC_opts.use_swmr ? H5F_ACC_SWMR_READ : 0), H5P_DEFAULT)) < 0){
-        HDfprintf(stderr, "H5Fopen failed\n");
-        return -1;
-    }
-    if((dsid = H5Dopen2(fid, progname_g, H5P_DEFAULT)) < 0){
-        HDfprintf(stderr, "H5Dopen2 failed\n");
-        return -1;
-    }
-#else
-    H5Drefresh(dsid);
-#endif
-    f_sid = H5Dget_space(dsid);    /* Get filespace handle first. */
-    if (H5Sget_simple_extent_dims(f_sid, dims, NULL) < 0){
-        HDfprintf(stderr, "H5Sget_simple_extent_dims got error\n");
-        return -1;
-    }
-    }
+        nplanes_seen=dims[0];
+
+        /* check if dataset has grown since last time (update dims) */
+        H5Drefresh(dsid);
+        f_sid = H5Dget_space(dsid);    /* Get filespace handle first. */
+        if (H5Sget_simple_extent_dims(f_sid, dims, NULL) < 0) {
+            HDfprintf(stderr, "H5Sget_simple_extent_dims got error\n");
+            return -1;
+        }
+    } /* end while (expecting more planes to read) */
 
-    /* Close the file */
-    if(H5Fclose(fid) < 0) {
+    if (H5Fclose(fid) < 0) {
         HDfprintf(stderr, "H5Fclose failed\n");
         return -1;
     }
@@ -631,7 +616,7 @@ int read_uc_file(hbool_t towait)
         return -1;
     else
         return 0;
-} /* read_uc_file() */
+} /* end read_uc_file() */
 
 #endif /* H5_HAVE_FORK */
 
diff --git a/test/vfd.c b/test/vfd.c
index e88d9bb..97995d2 100644
--- a/test/vfd.c
+++ b/test/vfd.c
@@ -25,6 +25,7 @@
 #define FAMILY_SIZE     (1*KB)
 #define FAMILY_SIZE2    (5*KB)
 #define MULTI_SIZE      128
+#define SPLITTER_SIZE   8 /* dimensions of a dataset */
 
 #define CORE_INCREMENT  (4*KB)
 #define CORE_PAGE_SIZE  (1024*KB)
@@ -59,6 +60,9 @@ const char *FILENAME[] = {
     "windows_file",      /*8*/
     "new_multi_file_v16",/*9*/
     "ro_s3_file",        /*10*/
+    "splitter_rw_file",  /*11*/
+    "splitter_wo_file",  /*12*/
+    "splitter.log",      /*13*/
     NULL
 };
 
@@ -66,8 +70,47 @@ const char *FILENAME[] = {
 
 #define COMPAT_BASENAME "family_v16_"
 #define MULTI_COMPAT_BASENAME "multi_file_v16"
+#define SPLITTER_DATASET_NAME "dataset"
+
+/* Macro: HEXPRINT()
+ * Helper macro to pretty-print hexadecimal output of a buffer of known size.
+ * Each line has the address of the first printed byte, and four columns of
+ * four-byte data.
+ */
+static int __k;
+#define HEXPRINT(size, buf)                                                   \
+for (__k = 0; __k < (size); __k++) {                                          \
+    if (__k % 16 == 0) {                                                      \
+        HDprintf("\n%04x", __k);                                              \
+    }                                                                         \
+    HDprintf((__k%4 == 0) ? "  %02X" : " %02X", (unsigned char)(buf)[__k]);   \
+} /* end #define HEXPRINT() */
 
 
+/* Helper structure to pass around dataset information.
+ */
+struct splitter_dataset_def {
+    void *buf;             /* contents of dataset */
+    const char *dset_name; /* dataset name, always added to root group */
+    hid_t mem_type_id;     /* datatype */
+    const hsize_t *dims;   /* dimensions */
+    int n_dims;            /* rank */
+};
+
+static int splitter_prepare_file_paths(H5FD_splitter_vfd_config_t *vfd_config,
+        char *filename_rw_out);
+static int splitter_create_single_file_at(const char *filename, hid_t fapl_id,
+        const struct splitter_dataset_def *data);
+static int splitter_compare_expected_data(hid_t file_id,
+        const struct splitter_dataset_def *data);
+static int run_splitter_test(const struct splitter_dataset_def *data,
+        hbool_t ignore_wo_errors, hbool_t provide_logfile_path,
+        hid_t sub_fapl_ids[2]);
+static int splitter_RO_test(const struct splitter_dataset_def *data,
+        hid_t child_fapl_id);
+static int splitter_tentative_open_test(hid_t child_fapl_id);
+static int file_exists(const char *filename, hid_t fapl_id);
+
 /*-------------------------------------------------------------------------
  * Function:    test_sec2
  *
@@ -859,7 +902,7 @@ test_family(void)
     hid_t       driver_id = -1;             /* ID for this VFD              */
     unsigned long driver_flags = 0;         /* VFD feature flags            */
     char        filename[1024];
-    char        dname[]="dataset";
+    char        dname[] = "dataset";
     unsigned int i, j;
     int         *fhandle=NULL, *fhandle2=NULL;
     int         **buf = NULL;
@@ -1263,7 +1306,7 @@ error:
     return FAIL;
 } /* end test_family_member_fapl() */
 
-
+
 /*-------------------------------------------------------------------------
  * Function:    test_multi_opens
  *
@@ -2179,6 +2222,1052 @@ error:
 #endif /* H5_HAVE_ROS3_VFD */
 } /* end test_ros3() */
 
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+ * Macro: SPLITTER_TEST_FAULT()
+ *
+ * utility macro, helps create stack-like backtrace on error.
+ * requires defined in the calling function:
+ *    * variable `int ret_value` (return -1 on error)`
+ *    * label `done` for exit on fault
+ * - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+ */
+#define SPLITTER_TEST_FAULT(mesg) { \
+    H5_FAILED();                    \
+    AT();                           \
+    HDfprintf(stderr, mesg);        \
+    H5Eprint2(H5E_DEFAULT, stderr); \
+    fflush(stderr);                 \
+    ret_value = -1;                 \
+    goto done;                      \
+}
+
+
+/*-------------------------------------------------------------------------
+ * Function:    compare_splitter_config_info
+ *
+ * Purpose:     Helper function to compare configuration info found in a
+ *              FAPL against a canonical structure.
+ *
+ * Return:      Success:  0, if config info in FAPL matches info structure.
+ *              Failure: -1, if difference detected.
+ *
+ *-------------------------------------------------------------------------
+ */
+static int
+compare_splitter_config_info(hid_t fapl_id, H5FD_splitter_vfd_config_t *info)
+{
+    int                         ret_value = 0;
+    H5FD_splitter_vfd_config_t  fetched_info;
+
+    fetched_info.magic = H5FD_SPLITTER_MAGIC;
+    fetched_info.version = H5FD_CURR_SPLITTER_VFD_CONFIG_VERSION;
+    fetched_info.rw_fapl_id = H5I_INVALID_HID;
+    fetched_info.wo_fapl_id = H5I_INVALID_HID;
+
+    if (H5Pget_fapl_splitter(fapl_id, &fetched_info) < 0) {
+        SPLITTER_TEST_FAULT("can't get splitter info\n");
+    }
+    if (info->rw_fapl_id == H5P_DEFAULT) {
+        if (H5Pget_driver(fetched_info.rw_fapl_id) != H5Pget_driver(H5P_FILE_ACCESS_DEFAULT)) {
+            SPLITTER_TEST_FAULT("Read-Write driver mismatch (default)\n");
+        }
+    }
+    else {
+        if (H5Pget_driver(fetched_info.rw_fapl_id) != H5Pget_driver(info->rw_fapl_id)) {
+            SPLITTER_TEST_FAULT("Read-Write driver mismatch\n");
+        }
+    }
+    if (info->wo_fapl_id == H5P_DEFAULT) {
+        if (H5Pget_driver(fetched_info.wo_fapl_id) != H5Pget_driver(H5P_FILE_ACCESS_DEFAULT)) {
+            SPLITTER_TEST_FAULT("Write-Only driver mismatch (default)\n");
+        }
+    }
+    else {
+        if (H5Pget_driver(fetched_info.wo_fapl_id) != H5Pget_driver(info->wo_fapl_id)) {
+            SPLITTER_TEST_FAULT("Write-Only driver mismatch\n");
+        }
+    }
+    if ( (HDstrlen(info->wo_path) != HDstrlen(fetched_info.wo_path)) ||
+         HDstrncmp(info->wo_path, fetched_info.wo_path, H5FD_SPLITTER_PATH_MAX))
+    {
+        HDfprintf(stderr, "MISMATCH: '%s' :: '%s'\n", info->wo_path, fetched_info.wo_path);
+        HEXPRINT(H5FD_SPLITTER_PATH_MAX, info->wo_path);
+        HEXPRINT(H5FD_SPLITTER_PATH_MAX, fetched_info.wo_path);
+        SPLITTER_TEST_FAULT("Write-Only file path mismatch\n");
+    }
+
+done:
+    return ret_value;
+} /* end compare_splitter_config_info() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    run_splitter_test
+ *
+ * Purpose:     Auxiliary function for test_splitter().
+ *
+ * Return:      Success:        0
+ *              Failure:        -1
+ *
+ * Description:
+ *              Perform basic open-write-close with the Splitter VFD.
+ *              Prior to operations, removes files from a previous run,
+ *              if they exist.
+ *              After writing, compares read-write and write-only files.
+ *              Includes FAPL sanity testing.
+ *
+ *-------------------------------------------------------------------------
+ */
+static int
+run_splitter_test(const struct splitter_dataset_def      *data,
+                  hbool_t ignore_wo_errors,
+                  hbool_t provide_logfile_path,
+                  hid_t   sub_fapl_ids[2])
+{
+    hid_t                       file_id     = H5I_INVALID_HID;
+    hid_t                       fapl_id     = H5I_INVALID_HID;
+    hid_t                       dset_id     = H5I_INVALID_HID;
+    hid_t                       space_id    = H5I_INVALID_HID;
+    hid_t                       fapl_id_out = H5I_INVALID_HID;
+    hid_t                       fapl_id_cpy = H5I_INVALID_HID;
+    H5FD_splitter_vfd_config_t  vfd_config;
+    char                        filename_rw[H5FD_SPLITTER_PATH_MAX + 1];
+    FILE                       *logfile     = NULL;
+    int                         ret_value   = 0;
+
+    vfd_config.magic = H5FD_SPLITTER_MAGIC;
+    vfd_config.version = H5FD_CURR_SPLITTER_VFD_CONFIG_VERSION;
+    vfd_config.ignore_wo_errs = ignore_wo_errors;
+    vfd_config.rw_fapl_id = sub_fapl_ids[0];
+    vfd_config.wo_fapl_id = sub_fapl_ids[1];
+
+    if (splitter_prepare_file_paths(&vfd_config, filename_rw) < 0) {
+        SPLITTER_TEST_FAULT("can't prepare file paths\n");
+    }
+
+    if (provide_logfile_path == FALSE) {
+        *vfd_config.log_file_path = '\0'; /* reset as empty string */
+    }
+
+    /* Create a new fapl to use the SPLITTER file driver */
+    if ((fapl_id = H5Pcreate(H5P_FILE_ACCESS)) == H5I_INVALID_HID) {
+        SPLITTER_TEST_FAULT("can't create FAPL ID\n");
+    }
+    if (H5Pset_fapl_splitter(fapl_id, &vfd_config) < 0) {
+        SPLITTER_TEST_FAULT("can't set splitter FAPL\n");
+    }
+    if (H5Pget_driver(fapl_id) != H5FD_SPLITTER) {
+        SPLITTER_TEST_FAULT("set FAPL not SPLITTER\n");
+    }
+
+    if (compare_splitter_config_info(fapl_id, &vfd_config) < 0) {
+        SPLITTER_TEST_FAULT("information mismatch\n");
+    }
+
+    /*
+     * Copy property list, light compare, and close the copy.
+     * Helps test driver-implemented FAPL-copying and library ID management.
+     */
+
+    fapl_id_cpy = H5Pcopy(fapl_id);
+    if (H5I_INVALID_HID == fapl_id_cpy) {
+        SPLITTER_TEST_FAULT("can't copy FAPL\n");
+    }
+    if (compare_splitter_config_info(fapl_id_cpy, &vfd_config) < 0) {
+        SPLITTER_TEST_FAULT("information mismatch\n");
+    }
+    if (H5Pclose(fapl_id_cpy) < 0) {
+        SPLITTER_TEST_FAULT("can't close fapl copy\n");
+    }
+
+    /*
+     * Proceed with test. Create file.
+     */
+    file_id = H5Fcreate(filename_rw, H5F_ACC_TRUNC, H5P_DEFAULT, fapl_id);
+    if (file_id < 0) {
+        SPLITTER_TEST_FAULT("can't create file\n");
+    }
+
+    /*
+     * Check driver from file
+     */
+
+    fapl_id_out = H5Fget_access_plist(file_id);
+    if (H5I_INVALID_HID == fapl_id_out) {
+        SPLITTER_TEST_FAULT("can't get file's FAPL\n");
+
+    }
+    if (H5Pget_driver(fapl_id_out) != H5FD_SPLITTER) {
+        SPLITTER_TEST_FAULT("wrong file FAPL driver\n");
+    }
+    if (compare_splitter_config_info(fapl_id_out, &vfd_config) < 0) {
+        SPLITTER_TEST_FAULT("information mismatch\n");
+    }
+    if (H5Pclose(fapl_id_out) < 0) {
+        SPLITTER_TEST_FAULT("can't close file's FAPL\n");
+    }
+
+    /*
+     * Create and write the dataset
+     */
+
+    space_id = H5Screate_simple(data->n_dims, data->dims, NULL);
+    if (space_id < 0) {
+        SPLITTER_TEST_FAULT("can't create dataspace\n");
+    }
+    dset_id = H5Dcreate2(file_id, data->dset_name, data->mem_type_id, space_id, H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
+    if (dset_id < 0) {
+        SPLITTER_TEST_FAULT("can't create dataset\n");
+    }
+    if (H5Dwrite(dset_id, data->mem_type_id, H5S_ALL, H5S_ALL, H5P_DEFAULT, data->buf) < 0) {
+        SPLITTER_TEST_FAULT("can't write data to dataset\n");
+    }
+
+    /* Close everything */
+    if (H5Dclose(dset_id) < 0) {
+        SPLITTER_TEST_FAULT("can't close dset\n");
+    }
+    if (H5Sclose(space_id) < 0) {
+        SPLITTER_TEST_FAULT("can't close space\n");
+    }
+    if (H5Pclose(fapl_id) < 0) {
+        SPLITTER_TEST_FAULT("can't close fapl\n");
+    }
+    if (H5Fclose(file_id) < 0) {
+        SPLITTER_TEST_FAULT("can't close file\n");
+    }
+
+    /* Verify that the R/W and W/O files are identical */
+    if (h5_compare_file_bytes(filename_rw, vfd_config.wo_path) < 0) {
+        SPLITTER_TEST_FAULT("files are not byte-for-byte equivalent\n");
+    }
+
+    /* Verify existence of logfile iff appropriate */
+    logfile = fopen(vfd_config.log_file_path, "r");
+    if ( (TRUE  == provide_logfile_path && NULL == logfile) ||
+         (FALSE == provide_logfile_path && NULL != logfile) )
+    {
+        SPLITTER_TEST_FAULT("no logfile when one was expected\n");
+    }
+
+done:
+    if (ret_value < 0) {
+        H5E_BEGIN_TRY {
+            (void)H5Dclose(dset_id);
+            (void)H5Sclose(space_id);
+            (void)H5Pclose(fapl_id_out);
+            (void)H5Pclose(fapl_id_cpy);
+            (void)H5Pclose(fapl_id);
+            (void)H5Fclose(file_id);
+        } H5E_END_TRY;
+    }
+    if (logfile != NULL) {
+        fclose(logfile);
+    }
+    return ret_value;
+
+} /* end run_splitter_test() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    driver_is_splitter_compatible
+ *
+ * Purpose:     Determine whether the driver set in the FAPL ID is compatible
+ *              with the Splitter VFD -- specificially, Write-Only channel.
+ *
+ * Return:      Success:        0
+ *              Failure:        -1
+ *
+ * Description: Attempts to put the given FAPL ID as the W/O channel.
+ *              Uses driver's own mechanisms to generate error, and catches
+ *              error.
+ *
+ *-------------------------------------------------------------------------
+ */
+static int
+driver_is_splitter_compatible(hid_t fapl_id)
+{
+    H5FD_splitter_vfd_config_t  vfd_config;
+    hid_t split_fapl_id = H5I_INVALID_HID;
+    herr_t ret;
+    int ret_value = 0;
+
+    split_fapl_id = H5Pcreate(H5P_FILE_ACCESS);
+    if (H5I_INVALID_HID == split_fapl_id) {
+        FAIL_PUTS_ERROR("Can't create contained FAPL");
+    }
+    vfd_config.magic = H5FD_SPLITTER_MAGIC;
+    vfd_config.version = H5FD_CURR_SPLITTER_VFD_CONFIG_VERSION;
+    vfd_config.ignore_wo_errs = FALSE;
+    vfd_config.rw_fapl_id = H5P_DEFAULT;
+    vfd_config.wo_fapl_id = fapl_id;
+    HDstrncpy(vfd_config.wo_path, "nonesuch", H5FD_SPLITTER_PATH_MAX);
+
+    H5E_BEGIN_TRY {
+        ret = H5Pset_fapl_splitter(split_fapl_id, &vfd_config);
+    } H5E_END_TRY;
+    if (SUCCEED == ret) {
+        ret_value = -1;
+    }
+
+    if (H5Pclose(split_fapl_id) < 0) {
+        FAIL_PUTS_ERROR("Can't close contained FAPL")
+    }
+    split_fapl_id = H5I_INVALID_HID;
+
+    return ret_value;
+
+error:
+    H5E_BEGIN_TRY {
+        (void)H5Pclose(split_fapl_id);
+    } H5E_END_TRY;
+    return -1;
+} /* end driver_is_splitter_compatible() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    splitter_RO_test
+ *
+ * Purpose:     Verify Splitter VFD with the Read-Only access flag.
+ *
+ * Return:      Success:        0
+ *              Failure:        -1
+ *
+ * Description: Attempt read-only opening of files with different
+ *              permutations of files already existing on-disk.
+ *
+ *-------------------------------------------------------------------------
+ */
+static int
+splitter_RO_test(
+        const struct splitter_dataset_def *data,
+        hid_t                              child_fapl_id)
+{
+    char        filename_rw[H5FD_SPLITTER_PATH_MAX + 1];
+    H5FD_splitter_vfd_config_t  vfd_config;
+    hid_t       fapl_id = H5I_INVALID_HID;
+    int         ret_value = 0;
+    hid_t       file_id = H5I_INVALID_HID;
+
+    vfd_config.magic = H5FD_SPLITTER_MAGIC;
+    vfd_config.version = H5FD_CURR_SPLITTER_VFD_CONFIG_VERSION;
+    vfd_config.ignore_wo_errs = FALSE;
+    vfd_config.rw_fapl_id = child_fapl_id;
+    vfd_config.wo_fapl_id = child_fapl_id;
+
+    if (splitter_prepare_file_paths(&vfd_config, filename_rw) < 0) {
+        SPLITTER_TEST_FAULT("can't prepare splitter file paths\n");
+    }
+
+    /* Create a new fapl to use the SPLITTER file driver */
+    fapl_id = H5Pcreate(H5P_FILE_ACCESS);
+    if (H5I_INVALID_HID == fapl_id) {
+        SPLITTER_TEST_FAULT("can't create FAPL ID\n");
+    }
+    if (H5Pset_fapl_splitter(fapl_id, &vfd_config) < 0) {
+        SPLITTER_TEST_FAULT("can't set splitter FAPL\n");
+    }
+    if (H5Pget_driver(fapl_id) != H5FD_SPLITTER) {
+        SPLITTER_TEST_FAULT("set FAPL not SPLITTER\n");
+    }
+
+    /* Attempt R/O open when both files are nonexistent
+     * Should fail.
+     */
+
+    H5E_BEGIN_TRY {
+        file_id = H5Fopen(filename_rw, H5F_ACC_RDONLY, fapl_id);
+    } H5E_END_TRY;
+    if (file_id >= 0) {
+        SPLITTER_TEST_FAULT("R/O open on nonexistent files unexpectedly successful\n");
+    }
+
+    /* Attempt R/O open when only W/O file exists
+     * Should fail.
+     */
+
+    if (splitter_create_single_file_at(vfd_config.wo_path, vfd_config.wo_fapl_id, data) < 0) {
+        SPLITTER_TEST_FAULT("can't write W/O file\n");
+    }
+    H5E_BEGIN_TRY {
+        file_id = H5Fopen(filename_rw, H5F_ACC_RDONLY, fapl_id);
+    } H5E_END_TRY;
+    if (file_id >= 0) {
+        SPLITTER_TEST_FAULT("R/O open with extant W/O file unexpectedly successful\n");
+    }
+    HDremove(vfd_config.wo_path);
+
+    /* Attempt R/O open when only R/W file exists
+     * Should fail.
+     */
+
+    if (splitter_create_single_file_at(filename_rw, vfd_config.rw_fapl_id, data) < 0) {
+        SPLITTER_TEST_FAULT("can't create R/W file\n");
+    }
+    H5E_BEGIN_TRY {
+        file_id = H5Fopen(filename_rw, H5F_ACC_RDONLY, fapl_id);
+    } H5E_END_TRY;
+    if (file_id >= 0) {
+        SPLITTER_TEST_FAULT("R/O open with extant R/W file unexpectedly successful\n");
+    }
+
+    /* Attempt R/O open when both R/W and W/O files exist
+     */
+
+    if (splitter_create_single_file_at(vfd_config.wo_path, vfd_config.wo_fapl_id, data) < 0) {
+        SPLITTER_TEST_FAULT("can't create W/O file\n");
+    }
+    file_id = H5Fopen(filename_rw, H5F_ACC_RDONLY, fapl_id);
+    if (file_id < 0) {
+        SPLITTER_TEST_FAULT("R/O open on two extant files failed\n");
+    }
+    if (splitter_compare_expected_data(file_id, data) < 0) {
+        SPLITTER_TEST_FAULT("data mismatch in R/W file\n");
+    }
+    if (H5Fclose(file_id) < 0) {
+        SPLITTER_TEST_FAULT("can't close file(s)\n");
+    }
+    file_id = H5I_INVALID_HID;
+
+    /* Cleanup
+     */
+
+    if (H5Pclose(fapl_id) < 0) {
+        SPLITTER_TEST_FAULT("can't close FAPL ID\n");
+    }
+    fapl_id = H5I_INVALID_HID;
+
+done:
+    if (ret_value < 0) {
+        H5E_BEGIN_TRY {
+            (void)H5Pclose(fapl_id);
+            (void)H5Fclose(file_id);
+        } H5E_END_TRY;
+    } /* end if error */
+    return ret_value;
+} /* end splitter_RO_test() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    splitter_prepare_file_paths
+ *
+ * Purpose:     Get file paths ready for use by the Splitter VFD tests.
+ *
+ * Return:      Success:        0
+ *              Failure:        -1
+ *
+ * Description:
+ *              Use h5_fixname to adjust the splitter-relevant file paths
+ *              from those given in FILENAMES.
+ *
+ *              REMOVES EXISTING FILES AT THE PATH LOCATIONS PRIOR TO RETURN.
+ *
+ *              The relevant file paths will be set in filename_rw_out and
+ *              inside the config structure (wo_path, log_file_path).
+ *
+ *              `filename_rw_out` must be at least H5FD_SPLITTER_PATH_MAX+1
+ *              characters long.
+ *
+ *              `vfd_config` must have its child FAPL IDs preset.
+ *
+ *-------------------------------------------------------------------------
+ */
+static int
+splitter_prepare_file_paths(H5FD_splitter_vfd_config_t *vfd_config, char *filename_rw_out)
+{
+    int ret_value = 0;
+
+    if (vfd_config == NULL || vfd_config->magic != H5FD_SPLITTER_MAGIC) {
+        SPLITTER_TEST_FAULT("invalid splitter config pointer\n");
+    }
+    if (filename_rw_out == NULL) {
+        SPLITTER_TEST_FAULT("NULL filename_rw pointer\n");
+    }
+
+    /* TODO: sanity-check fapl IDs? */
+
+    /* Build the r/w file, w/o file, and the log file paths.
+     * Output is stored in the associated string pointers.
+     */
+    h5_fixname(FILENAME[11], vfd_config->rw_fapl_id, filename_rw_out, H5FD_SPLITTER_PATH_MAX);
+    h5_fixname(FILENAME[12], vfd_config->wo_fapl_id, vfd_config->wo_path, H5FD_SPLITTER_PATH_MAX);
+    h5_fixname_no_suffix(FILENAME[13], vfd_config->wo_fapl_id, vfd_config->log_file_path, H5FD_SPLITTER_PATH_MAX);
+
+    /* Delete any existing files on disk.
+     */
+    HDremove(filename_rw_out);
+    HDremove(vfd_config->wo_path);
+    HDremove(vfd_config->log_file_path);
+
+done:
+    return ret_value;
+} /* end splitter_prepare_file_paths() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    splitter_crate_single_file_at
+ *
+ * Purpose:     Create a file, optionally w/ dataset.
+ *
+ * Return:      Success:        0
+ *              Failure:        -1
+ *
+ * Description:
+ *              Create a file at the given location with the given FAPL,
+ *              and write data as defined in `data` in a pre-determined location in the file.
+ *
+ *              If the dataset definition pointer is NULL, no data is written
+ *              to the file.
+ *
+ *              Will always overwrite an existing file with the given name/path.
+ *
+ *-------------------------------------------------------------------------
+ */
+static int
+splitter_create_single_file_at(
+        const char     *filename,
+        hid_t           fapl_id,
+        const struct splitter_dataset_def *data)
+{
+    hid_t       file_id = H5I_INVALID_HID;
+    hid_t       space_id = H5I_INVALID_HID;
+    hid_t       dset_id = H5I_INVALID_HID;
+    int         ret_value = 0;
+
+    if (filename == NULL || *filename == '\0') {
+        SPLITTER_TEST_FAULT("filename is invalid\n");
+    }
+    /* TODO: sanity-check fapl id? */
+
+    file_id = H5Fcreate(filename, H5F_ACC_TRUNC, H5P_DEFAULT, fapl_id);
+    if (file_id < 0) {
+        SPLITTER_TEST_FAULT("can't create file\n");
+    }
+
+    if (data) {
+        /* TODO: sanity-check data, if it exists? */
+        space_id = H5Screate_simple(data->n_dims, data->dims, NULL);
+        if (space_id < 0) {
+            SPLITTER_TEST_FAULT("can't create dataspace\n");
+        }
+
+        dset_id = H5Dcreate2(
+                file_id,
+                data->dset_name,
+                data->mem_type_id,
+                space_id,
+                H5P_DEFAULT,
+                H5P_DEFAULT,
+                H5P_DEFAULT);
+        if (dset_id < 0) {
+            SPLITTER_TEST_FAULT("can't create dataset\n");
+        }
+
+        if (H5Dwrite(dset_id, data->mem_type_id, H5S_ALL, H5S_ALL, H5P_DEFAULT, data->buf) < 0) {
+            SPLITTER_TEST_FAULT("can't write data to dataset\n");
+        }
+
+        if (H5Dclose(dset_id) < 0) {
+            SPLITTER_TEST_FAULT("can't close dset\n");
+        }
+        if (H5Sclose(space_id) < 0) {
+            SPLITTER_TEST_FAULT("can't close space\n");
+        }
+    } /* end if data definition is provided */
+
+    if (H5Fclose(file_id) < 0) {
+        SPLITTER_TEST_FAULT("can't close file\n");
+    }
+
+done:
+    if (ret_value < 0) {
+        H5E_BEGIN_TRY {
+            (void)H5Dclose(dset_id);
+            (void)H5Sclose(space_id);
+            (void)H5Fclose(file_id);
+        } H5E_END_TRY;
+    } /* end if error */
+    return ret_value;
+} /* end splitter_create_single_file_at() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    splitter_compare_expected_data
+ *
+ * Purpose:     Compare data within a predermined dataset.
+ *
+ * Return:      Success:        0
+ *              Failure:        -1
+ *
+ * Description: Read data from the file at a predetermined location, and
+ *              compare its contents byte-for-byte with that expected in
+ *              the `data` definition structure.
+ *
+ *-------------------------------------------------------------------------
+ */
+static int
+splitter_compare_expected_data(hid_t file_id,
+                               const struct splitter_dataset_def *data)
+{
+    hid_t dset_id = H5I_INVALID_HID;
+    int buf[SPLITTER_SIZE][SPLITTER_SIZE];
+    int expected[SPLITTER_SIZE][SPLITTER_SIZE];
+    size_t i = 0;
+    size_t j = 0;
+    int ret_value = 0;
+
+    if (sizeof((void *)buf) != sizeof(data->buf)) {
+        SPLITTER_TEST_FAULT("invariant size of expected data does not match that received!\n");
+    }
+    HDmemcpy(expected, data->buf, sizeof(expected));
+
+    dset_id = H5Dopen2(file_id, data->dset_name, H5P_DEFAULT);
+    if (dset_id < 0) {
+        SPLITTER_TEST_FAULT("can't open dataset\n");
+    }
+
+    if (H5Dread(dset_id, data->mem_type_id, H5S_ALL, H5S_ALL, H5P_DEFAULT, (void *)buf) < 0) {
+        SPLITTER_TEST_FAULT("can't read dataset\n");
+    }
+
+    for (i=0; i < SPLITTER_SIZE; i++) {
+        for (j=0; j < SPLITTER_SIZE; j++) {
+            if (buf[i][j] != expected[i][j]) {
+                SPLITTER_TEST_FAULT("mismatch in expected data\n");
+            }
+        }
+    }
+
+    if (H5Dclose(dset_id) < 0) {
+        SPLITTER_TEST_FAULT("can't close dataset\n");
+    }
+
+done:
+    if (ret_value < 0) {
+        H5E_BEGIN_TRY {
+            (void)H5Dclose(dset_id);
+        } H5E_END_TRY;
+    }
+    return ret_value;
+} /* end splitter_compare_expected_data() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    splitter_tentative_open_test()
+ *
+ * Purpose:     Verifies Splitter behavior with "tentative" H5F_open.
+ *
+ * Return:      Success:        0
+ *              Failure:        -1
+ *
+ * Description:
+ *              H5F_open() has a two-stage opening process when given a
+ *              Read/Write access flag -- first it performs a "tentative
+ *              open", where it checks to see whether files already exist
+ *              on the system, done in such a way as to not "alter its state"
+ *              (i.e., truncate).
+ *              This can cause problems with the Splitter VFD, as the
+ *              file on the R/W channel might exist already, but that on the
+ *              W/O channel will not, and vice-versa.
+ *
+ *              This test exists to verify that in any event, files will be
+ *              created as required.
+ *
+ *-------------------------------------------------------------------------
+ */
+static int
+splitter_tentative_open_test(hid_t child_fapl_id)
+{
+    char        filename_rw[H5FD_SPLITTER_PATH_MAX + 1];
+    H5FD_splitter_vfd_config_t  vfd_config;
+    hid_t       fapl_id = H5I_INVALID_HID;
+    hid_t       file_id = H5I_INVALID_HID;
+    int         buf[SPLITTER_SIZE][SPLITTER_SIZE]; /* for comparison */
+    hsize_t     dims[2]        = { SPLITTER_SIZE, SPLITTER_SIZE }; /* for comparison */
+    int         i              = 0; /* for comparison */
+    int         j              = 0; /* for comparison */
+    struct splitter_dataset_def data; /* for comparison */
+    int         ret_value = 0;
+
+    /* pre-fill data buffer to write */
+    for (i=0; i < SPLITTER_SIZE; i++) {
+        for (j=0; j < SPLITTER_SIZE; j++) {
+            buf[i][j] = i*100+j;
+        }
+    }
+
+    /* Dataset info */
+    data.buf = (void *)buf;
+    data.mem_type_id = H5T_NATIVE_INT;
+    data.dims = dims;
+    data.n_dims = 2;
+    data.dset_name = SPLITTER_DATASET_NAME;
+
+    vfd_config.magic = H5FD_SPLITTER_MAGIC;
+    vfd_config.version = H5FD_CURR_SPLITTER_VFD_CONFIG_VERSION;
+    vfd_config.ignore_wo_errs = FALSE;
+    vfd_config.rw_fapl_id = child_fapl_id;
+    vfd_config.wo_fapl_id = child_fapl_id;
+
+    if (splitter_prepare_file_paths(&vfd_config, filename_rw) < 0) {
+        SPLITTER_TEST_FAULT("can't prepare splitter file paths\n");
+    }
+
+    /* Create a new fapl to use the SPLITTER file driver */
+    if ((fapl_id = H5Pcreate(H5P_FILE_ACCESS)) == H5I_INVALID_HID) {
+        SPLITTER_TEST_FAULT("can't create FAPL ID\n");
+    }
+    if (H5Pset_fapl_splitter(fapl_id, &vfd_config) < 0) {
+        SPLITTER_TEST_FAULT("can't set splitter FAPL\n");
+    }
+    if (H5Pget_driver(fapl_id) != H5FD_SPLITTER) {
+        SPLITTER_TEST_FAULT("set FAPL not SPLITTER\n");
+    }
+
+    /* H5Fopen() with RDWR access.
+     * Neither file exist already
+     * Should fail.
+     */
+
+    H5E_BEGIN_TRY {
+        file_id = H5Fopen(filename_rw, H5F_ACC_RDWR, fapl_id);
+    } H5E_END_TRY;
+    if (file_id != H5I_INVALID_HID) {
+        SPLITTER_TEST_FAULT("open with both nonexistent files unexpectedly succeeded\n");
+    }
+    if (file_exists(filename_rw, child_fapl_id)) {
+        SPLITTER_TEST_FAULT("R/W file unexpectedly created\n");
+    }
+    if (file_exists(vfd_config.wo_path, child_fapl_id)) {
+        SPLITTER_TEST_FAULT("W/O file unexpectedly created\n");
+    }
+
+    /* H5Fopen() with RDWR access.
+     * W/O file exists already.
+     * Should fail.
+     */
+
+    if (splitter_create_single_file_at(vfd_config.wo_path, child_fapl_id, &data) < 0) {
+        SPLITTER_TEST_FAULT("can't write W/O file\n");
+    }
+    H5E_BEGIN_TRY {
+        file_id = H5Fopen(filename_rw, H5F_ACC_RDWR, fapl_id);
+    } H5E_END_TRY;
+    if (file_id != H5I_INVALID_HID) {
+        SPLITTER_TEST_FAULT("open with nonexistent R/W file unexpectedly succeeded\n");
+    }
+    if (file_exists(filename_rw, child_fapl_id)) {
+        SPLITTER_TEST_FAULT("R/W file unexpectedly created\n");
+    }
+    if (!file_exists(vfd_config.wo_path, child_fapl_id)) {
+        SPLITTER_TEST_FAULT("W/O file mysteriously disappeared\n");
+    }
+    HDremove(vfd_config.wo_path);
+    if (file_exists(vfd_config.wo_path, child_fapl_id)) {
+        SPLITTER_TEST_FAULT("failed to remove W/O file\n");
+    }
+
+    /* H5Fopen() with RDWR access.
+     * R/W file exists already.
+     * Should fail.
+     */
+
+    if (splitter_create_single_file_at(filename_rw, child_fapl_id, &data) < 0) {
+        SPLITTER_TEST_FAULT("can't write R/W file\n");
+    }
+    H5E_BEGIN_TRY {
+        file_id = H5Fopen(filename_rw, H5F_ACC_RDWR, fapl_id);
+    } H5E_END_TRY;
+    if (file_id != H5I_INVALID_HID) {
+        SPLITTER_TEST_FAULT("open with nonexistent W/O unexpectedly succeeded\n");
+    }
+    if (!file_exists(filename_rw, child_fapl_id)) {
+        SPLITTER_TEST_FAULT("R/W file mysteriously disappeared\n");
+    }
+    if (file_exists(vfd_config.wo_path, child_fapl_id)) {
+        SPLITTER_TEST_FAULT("W/O file unexpectedly created\n");
+    }
+
+    /* H5Fopen() with RDWR access.
+     * Both files already exist.
+     */
+
+    if (splitter_create_single_file_at(vfd_config.wo_path, child_fapl_id, &data) < 0) {
+        SPLITTER_TEST_FAULT("can't write W/O file\n");
+    }
+    file_id = H5Fopen(filename_rw, H5F_ACC_RDWR, fapl_id);
+    if (file_id == H5I_INVALID_HID) {
+        SPLITTER_TEST_FAULT("file-open failed with both present\n");
+    }
+    /* Open successful; close file then inspect presence again */
+    if (H5Fclose(file_id) < 0) {
+        SPLITTER_TEST_FAULT("can't close file ID\n");
+    }
+    if (!file_exists(filename_rw, child_fapl_id)) {
+        SPLITTER_TEST_FAULT("R/W file mysteriously disappared\n");
+    }
+    if (!file_exists(vfd_config.wo_path, child_fapl_id)) {
+        SPLITTER_TEST_FAULT("W/O file mysteriously disappeared\n");
+    }
+    if (h5_compare_file_bytes(filename_rw, vfd_config.wo_path) < 0) {
+        SPLITTER_TEST_FAULT("files are not byte-for-byte equivalent\n");
+    }
+
+    /* H5Fcreate() with TRUNC access.
+     * Both files already exist.
+     */
+
+    file_id = H5Fcreate(filename_rw, H5F_ACC_TRUNC, H5P_DEFAULT, fapl_id);
+    if (file_id == H5I_INVALID_HID) {
+        SPLITTER_TEST_FAULT("file-open failed with both present\n");
+    }
+    /* Open successful; close file then inspect presence again */
+    if (H5Fclose(file_id) < 0) {
+        SPLITTER_TEST_FAULT("can't close file ID\n");
+    }
+    if (!file_exists(filename_rw, child_fapl_id)) {
+        SPLITTER_TEST_FAULT("R/W file mysteriously disappared\n");
+    }
+    if (!file_exists(vfd_config.wo_path, child_fapl_id)) {
+        SPLITTER_TEST_FAULT("W/O file mysteriously disappeared\n");
+    }
+    if (h5_compare_file_bytes(filename_rw, vfd_config.wo_path) < 0) {
+        SPLITTER_TEST_FAULT("files are not byte-for-byte equivalent\n");
+    }
+
+    /* H5Fcreate() with TRUNC access.
+     * R/W already exists.
+     */
+
+    HDremove(filename_rw);
+    HDremove(vfd_config.wo_path);
+    if (splitter_create_single_file_at(filename_rw, child_fapl_id, &data) < 0) {
+        SPLITTER_TEST_FAULT("can't write R/W file\n");
+    }
+
+    if (file_exists(vfd_config.wo_path, child_fapl_id)) {
+        SPLITTER_TEST_FAULT("failed to remove W/O file\n");
+    }
+    file_id = H5Fcreate(filename_rw, H5F_ACC_TRUNC, H5P_DEFAULT, fapl_id);
+    if (file_id == H5I_INVALID_HID) {
+        SPLITTER_TEST_FAULT("file-open failed with both present\n");
+    }
+    /* Open successful; close file then inspect presence again */
+    if (H5Fclose(file_id) < 0) {
+        SPLITTER_TEST_FAULT("can't close file ID\n");
+    }
+    if (!file_exists(filename_rw, child_fapl_id)) {
+        SPLITTER_TEST_FAULT("R/W file mysteriously disappared\n");
+    }
+    if (!file_exists(vfd_config.wo_path, child_fapl_id)) {
+        SPLITTER_TEST_FAULT("W/O file mysteriously disappeared\n");
+    }
+    if (h5_compare_file_bytes(filename_rw, vfd_config.wo_path) < 0) {
+        SPLITTER_TEST_FAULT("files are not byte-for-byte equivalent\n");
+    }
+
+    /* H5Fcreate() with TRUNC access.
+     * W/O already exists.
+     */
+
+    HDremove(filename_rw);
+    HDremove(vfd_config.wo_path);
+    if (splitter_create_single_file_at(vfd_config.wo_path, child_fapl_id, &data) < 0) {
+        SPLITTER_TEST_FAULT("can't write R/W file\n");
+    }
+
+    if (file_exists(filename_rw, child_fapl_id)) {
+        SPLITTER_TEST_FAULT("failed to remove R/W file\n");
+    }
+    file_id = H5Fcreate(filename_rw, H5F_ACC_TRUNC, H5P_DEFAULT, fapl_id);
+    if (file_id == H5I_INVALID_HID) {
+        SPLITTER_TEST_FAULT("file-open failed with both present\n");
+    }
+    /* Open successful; close file then inspect presence again */
+    if (H5Fclose(file_id) < 0) {
+        SPLITTER_TEST_FAULT("can't close file ID\n");
+    }
+    if (!file_exists(filename_rw, child_fapl_id)) {
+        SPLITTER_TEST_FAULT("R/W file mysteriously disappared\n");
+    }
+    if (!file_exists(vfd_config.wo_path, child_fapl_id)) {
+        SPLITTER_TEST_FAULT("W/O file mysteriously disappeared\n");
+    }
+    if (h5_compare_file_bytes(filename_rw, vfd_config.wo_path) < 0) {
+        SPLITTER_TEST_FAULT("files are not byte-for-byte equivalent\n");
+    }
+
+    /* H5Fcreate with both files absent is tested elsewhere */
+
+    /* Cleanup
+     */
+
+    if (H5Pclose(fapl_id) < 0) {
+        SPLITTER_TEST_FAULT("can't close splitter FAPL ID\n");
+    }
+
+done:
+    if (ret_value < 0) {
+        H5E_BEGIN_TRY {
+            (void)H5Pclose(fapl_id);
+            (void)H5Fclose(file_id);
+        } H5E_END_TRY;
+    } /* end if error */
+    return ret_value;
+} /* end splitter_tentative_open_test() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    file_exists()
+ *
+ * Purpose:     Determine whether a file exists on-system
+ *
+ * Return:      Non-zero (1) if it exists (H5Fopen successful),
+ *              zero (0) if absent (cannot be opened).
+ *
+ * Description: Attempt H5Fopen with the given FAPL ID and RDONLY access flag.
+ *
+ *-------------------------------------------------------------------------
+ */
+static int
+file_exists(const char *filename, hid_t fapl_id)
+{
+    hid_t file_id = H5I_INVALID_HID;
+    int ret_value = 0;
+
+    H5E_BEGIN_TRY {
+        file_id = H5Fopen(filename, H5F_ACC_RDONLY, fapl_id);
+    } H5E_END_TRY;
+    if (file_id != H5I_INVALID_HID) {
+        ret_value = 1;
+        if (H5Fclose(file_id) < 0) {
+            FAIL_PUTS_ERROR("can't close file ID\n");
+        }
+    }
+
+    return ret_value;
+
+error:
+    H5E_BEGIN_TRY {
+        (void)H5Fclose(file_id);
+    } H5E_END_TRY;
+    return ret_value;
+} /* end file_exists() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    test_splitter
+ *
+ * Purpose:     Tests the Splitter VFD
+ *
+ * Return:      Success:        0
+ *              Failure:        -1
+ *
+ * Description:
+ *              This test function uses the Splitter VFD to produce a r/w
+ *              file and a w/o file. It will verify that the two files
+ *              are identical.
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+test_splitter(void)
+{
+    int         buf[SPLITTER_SIZE][SPLITTER_SIZE];
+    hsize_t     dims[2]        = { SPLITTER_SIZE, SPLITTER_SIZE };
+    hid_t       child_fapl_id  = H5I_INVALID_HID;
+    int         i              = 0;
+    int         j              = 0;
+    struct splitter_dataset_def data;
+
+    TESTING("SPLITTER file driver");
+
+    /* pre-fill data buffer to write */
+    for (i=0; i < SPLITTER_SIZE; i++) {
+        for (j=0; j < SPLITTER_SIZE; j++) {
+            buf[i][j] = i*100+j;
+        }
+    }
+
+    /* Dataset info */
+    data.buf = (void *)buf;
+    data.mem_type_id = H5T_NATIVE_INT;
+    data.dims = dims;
+    data.n_dims = 2;
+    data.dset_name = SPLITTER_DATASET_NAME;
+
+    /* Stand-in for manual FAPL creation
+     * Enables verification with arbitrary VFDs via `make check-vfd`
+     */
+    child_fapl_id = h5_fileaccess();
+    if (child_fapl_id < 0) {
+        TEST_ERROR;
+    }
+
+    if (!driver_is_splitter_compatible(child_fapl_id)) {
+        SKIPPED();
+        HDprintf("  given driver is not Splitter W/O compatible.\n");
+        return 0;
+    }
+
+    /* Test Read-Only access, including when a file on the W/O channel
+     * does not exist.
+     */
+    if (splitter_RO_test(&data, child_fapl_id) < 0) {
+        TEST_ERROR;
+    }
+
+    /* Test opening of files when the W/O channel does not exist.
+     */
+    if (splitter_tentative_open_test(child_fapl_id) < 0) {
+        TEST_ERROR;
+    }
+
+
+    /* Test file creation, utilizing different child FAPLs (default vs.
+     * specified), logfile, and Write Channel error ignoring behavior.
+     */
+    for (i=0; i < 4; i++) {
+        hbool_t ignore_wo_errors = (i & 1) ? TRUE : FALSE;
+        hbool_t provide_logfile_path = (i & 2) ? TRUE : FALSE;
+        hid_t   child_fapl_ids[2] = { H5P_DEFAULT, H5P_DEFAULT };
+
+        /* Test child driver definition/default combination */
+        for (j=0; j < 4; j++) {
+
+            child_fapl_ids[0] = (j & 1) ? child_fapl_id : H5P_DEFAULT;
+            child_fapl_ids[1] = (j & 2) ? child_fapl_id : H5P_DEFAULT;
+
+            if (run_splitter_test(&data, ignore_wo_errors, provide_logfile_path, child_fapl_ids) < 0) {
+                TEST_ERROR;
+            }
+
+        } /* end for child fapl definition/pairing */
+
+    } /* end for behavior-flag loops */
+
+/* TODO: SWMR open? */
+/* Concurrent opens with both drivers using the Splitter */
+
+
+    if (H5Pclose(child_fapl_id) == FAIL) {
+        TEST_ERROR;
+    }
+
+    PASSED();
+    return 0;
+
+error:
+    if (child_fapl_id != H5I_INVALID_HID) {
+        (void)H5Pclose(child_fapl_id);
+    }
+    return -1;
+} /* end test_splitter() */
+
+#undef SPLITTER_TEST_FAULT
+
+
 /*-------------------------------------------------------------------------
  * Function:    main
  *
@@ -2187,9 +3276,6 @@ error:
  * Return:      Success:        0
  *              Failure:        1
  *
- * Programmer:  Raymond Lu
- *              Tuesday, Sept 24, 2002
- *
  *-------------------------------------------------------------------------
  */
 int
@@ -2213,6 +3299,7 @@ main(void)
     nerrors += test_stdio() < 0          ? 1 : 0;
     nerrors += test_windows() < 0        ? 1 : 0;
     nerrors += test_ros3() < 0           ? 1 : 0;
+    nerrors += test_splitter() < 0       ? 1 : 0;
 
     if(nerrors) {
         HDprintf("***** %d Virtual File Driver TEST%s FAILED! *****\n",