Issue #21750: Further fixup to be styled like other mock APIs.

1 files changed, 5 insertions, 3 deletions

diff --git a/Doc/library/unittest.mock.rst b/Doc/library/unittest.mock.rst
index 8346cb9..fcd7727 100644
--- a/Doc/library/unittest.mock.rst
+++ b/Doc/library/unittest.mock.rst
@@ -1995,9 +1995,11 @@ mock_open
     :meth:`~io.IOBase.readline`, and :meth:`~io.IOBase.readlines` methods
     of the file handle to return.  Calls to those methods will take data from
     *read_data* until it is depleted.  The mock of these methods is pretty
-    simplistic.  If you need more control over the data that you are feeding to
-    the tested code you will need to customize this mock for yourself.
-    *read_data* is an empty string by default.
+    simplistic: every time the *mock* is called, the *read_data* is rewound to
+    the start.  If you need more control over the data that you are feeding to
+    the tested code you will need to customize this mock for yourself.  When that
+    is insufficient, one of the in-memory filesystem packages on `PyPI
+    <https://pypi.python.org/pypi>`_ can offer a realistic filesystem for testing.
 
 Using :func:`open` as a context manager is a great way to ensure your file handles
 are closed properly and is becoming common::