Index: Misc/NEWS
===================================================================
--- Misc/NEWS	(revision 86636)
+++ Misc/NEWS	(working copy)
@@ -86,6 +86,9 @@
 - Issue #10429: IMAP.starttls() stored the capabilities as bytes objects,
   rather than strings.
 
+- Issue #10470: 'python -m unittest' will now run test discovery by default,
+  when no extra arguments have been provided.
+
 C-API
 -----
 
Index: Doc/library/unittest.rst
===================================================================
--- Doc/library/unittest.rst	(revision 86636)
+++ Doc/library/unittest.rst	(working copy)
@@ -208,6 +208,12 @@
 
    python -m unittest -v test_module
 
+When executed without arguments::
+
+   python -m unittest
+
+The module performs :ref:`unittest-test-discovery`.
+
 For a list of all the command-line options::
 
    python -m unittest -h
Index: Lib/unittest/test/test_program.py
===================================================================
--- Lib/unittest/test/test_program.py	(revision 86636)
+++ Lib/unittest/test/test_program.py	(working copy)
@@ -64,16 +64,25 @@
             return self.suiteClass(
                 [self.loadTestsFromTestCase(Test_TestProgram.FooBar)])
 
+    def register_restore_path(self):
+        """Register a function on .addCleanup that restores sys.path to its
+           current condition.
+        """
+        orig_sys_path = sys.path[:]
+        def restore_path():
+            sys.path[:] = orig_sys_path
+        self.addCleanup(restore_path)
 
     def test_NonExit(self):
+        self.register_restore_path()
         program = unittest.main(exit=False,
                                 argv=["foobar"],
                                 testRunner=unittest.TextTestRunner(stream=io.StringIO()),
                                 testLoader=self.FooBarLoader())
         self.assertTrue(hasattr(program, 'result'))
 
-
     def test_Exit(self):
+        self.register_restore_path()
         self.assertRaises(
             SystemExit,
             unittest.main,
@@ -84,6 +93,7 @@
 
 
     def test_ExitAsDefault(self):
+        self.register_restore_path()
         self.assertRaises(
             SystemExit,
             unittest.main,
Index: Lib/unittest/main.py
===================================================================
--- Lib/unittest/main.py	(revision 86636)
+++ Lib/unittest/main.py	(working copy)
@@ -109,7 +109,9 @@
         sys.exit(2)
 
     def parseArgs(self, argv):
-        if len(argv) > 1 and argv[1].lower() == 'discover':
+        # Run test discovery: either 'discover' is the fist argument, or by
+        # default, when no arguments are specified.
+        if len(argv) == 1 or (len(argv) > 1 and argv[1].lower() == 'discover'):
             self._do_discovery(argv[2:])
             return