GH-71383: IDLE - Document testing subsets of modules (#104463)

Lib/idlelib/idle_test/README.txt

@@ -146,14 +146,17 @@ python -m unittest -v idlelib.idle_test
 python -m test -v -ugui test_idle
 python -m test.test_idle
 
-The idle tests are 'discovered' by
-idlelib.idle_test.__init__.load_tests, which is also imported into
-test.test_idle. Normally, neither file should be changed when working on
-individual test modules. The third command runs unittest indirectly
-through regrtest. The same happens when the entire test suite is run
-with 'python -m test'. So that command must work for buildbots to stay
-green. Idle tests must not disturb the environment in a way that makes
-other tests fail (issue 18081).
+IDLE tests are 'discovered' by idlelib.idle_test.__init__.load_tests
+when this is imported into test.test_idle. Normally, neither file
+should be changed when working on individual test modules. The third
+command runs unittest indirectly through regrtest. The same happens when
+the entire test suite is run with 'python -m test'. So that command must
+work for buildbots to stay green. IDLE tests must not disturb the
+environment in a way that makes other tests fail (GH-62281).
+
+To test subsets of modules, see idlelib.idle_test.__init__.  This
+can be used to find refleaks or possible sources of "Theme changed"
+tcl messages (GH-71383).
 
 To run an individual Testcase or test method, extend the dotted name
 given to unittest on the command line or use the test -m option.  The

Lib/idlelib/idle_test/__init__.py

@@ -1,17 +1,27 @@
-'''idlelib.idle_test is a private implementation of test.test_idle,
-which tests the IDLE application as part of the stdlib test suite.
-Run IDLE tests alone with "python -m test.test_idle".
-Starting with Python 3.6, IDLE requires tcl/tk 8.5 or later.
+"""idlelib.idle_test implements test.test_idle, which tests the IDLE
+application as part of the stdlib test suite.
+Run IDLE tests alone with "python -m test.test_idle (-v)".
 
 This package and its contained modules are subject to change and
 any direct use is at your own risk.
-'''
+"""
 from os.path import dirname
 
+# test_idle imports load_tests for test discovery (default all).
+# To run subsets of idlelib module tests, insert '[<chars>]' after '_'.
+# Example: insert '[ac]' for modules beginning with 'a' or 'c'.
+# Additional .discover/.addTest pairs with separate inserts work.
+# Example: pairs with 'c' and 'g' test c* files and grep.
+
 def load_tests(loader, standard_tests, pattern):
     this_dir = dirname(__file__)
     top_dir = dirname(dirname(this_dir))
-    package_tests = loader.discover(start_dir=this_dir, pattern='test*.py',
+    module_tests = loader.discover(start_dir=this_dir,
+                                    pattern='test_*.py',  # Insert here.
                                     top_level_dir=top_dir)
-    standard_tests.addTests(package_tests)
+    standard_tests.addTests(module_tests)
+##    module_tests = loader.discover(start_dir=this_dir,
+##                                    pattern='test_*.py',  # Insert here.
+##                                    top_level_dir=top_dir)
+##    standard_tests.addTests(module_tests)
     return standard_tests

Lib/test/test_idle.py

@@ -5,12 +5,8 @@ from test.support import check_sanitizer
 if check_sanitizer(address=True, memory=True):
     raise unittest.SkipTest("Tests involving libX11 can SEGFAULT on ASAN/MSAN builds")
 
-# Skip test_idle if _tkinter wasn't built, if tkinter is missing,
-# if tcl/tk is not the 8.5+ needed for ttk widgets,
-# or if idlelib is missing (not installed).
+# Skip test_idle if _tkinter, tkinter, or idlelib are missing.
 tk = import_module('tkinter')  # Also imports _tkinter.
-if tk.TkVersion < 8.5:
-    raise unittest.SkipTest("IDLE requires tk 8.5 or later.")
 idlelib = import_module('idlelib')
 
 # Before importing and executing more of idlelib,