1 files changed, 14 insertions, 0 deletions
diff --git a/Lib/test/test_imaplib.py b/Lib/test/test_imaplib.py
index f16bacd..a0b598d 100644
--- a/Lib/test/test_imaplib.py
+++ b/Lib/test/test_imaplib.py
@@ -1,6 +1,7 @@
 from test import support
 
 from contextlib import contextmanager
+import errno
 import imaplib
 import os.path
 import socketserver
@@ -69,6 +70,19 @@ class TestImaplib(unittest.TestCase):
         for t in self.timevalues():
             imaplib.Time2Internaldate(t)
 
+    def test_imap4_host_default_value(self):
+        expected_errnos = [
+            # This is the exception that should be raised.
+            errno.ECONNREFUSED,
+        ]
+        if hasattr(errno, 'EADDRNOTAVAIL'):
+            # socket.create_connection() fails randomly with
+            # EADDRNOTAVAIL on Travis CI.
+            expected_errnos.append(errno.EADDRNOTAVAIL)
+        with self.assertRaises(OSError) as cm:
+            imaplib.IMAP4()
+        self.assertIn(cm.exception.errno, expected_errnos)
+
 
 if ssl:
     class SecureTCPServer(socketserver.TCPServer):