From 339f2608671e6b7bd8494e3dcade0b03cb09c9b5 Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Tue, 5 Sep 2023 20:34:04 +0300
Subject: [PATCH 01/13] gh-108927: Do not remove tested modules from
 sys.modules

It breaks import machinery if the test module has submodules used in
other tests.
---
 Lib/test/libregrtest/runtest.py                               | 4 ----
 .../next/Tests/2023-09-05-20-46-35.gh-issue-108927.TpwWav.rst | 2 ++
 2 files changed, 2 insertions(+), 4 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Tests/2023-09-05-20-46-35.gh-issue-108927.TpwWav.rst

diff --git a/Lib/test/libregrtest/runtest.py b/Lib/test/libregrtest/runtest.py
index 16ae04191da768..795cd7f9bde853 100644
--- a/Lib/test/libregrtest/runtest.py
+++ b/Lib/test/libregrtest/runtest.py
@@ -434,10 +434,6 @@ def regrtest_runner(result, test_func, ns) -> None:
 def _load_run_test(result: TestResult, ns: Namespace) -> None:
     # Load the test function, run the test function.
     module_name = abs_module_name(result.test_name, ns.testdir)
-
-    # Remove the module from sys.module to reload it if it was already imported
-    sys.modules.pop(module_name, None)
-
     test_mod = importlib.import_module(module_name)
 
     if hasattr(test_mod, "test_main"):
diff --git a/Misc/NEWS.d/next/Tests/2023-09-05-20-46-35.gh-issue-108927.TpwWav.rst b/Misc/NEWS.d/next/Tests/2023-09-05-20-46-35.gh-issue-108927.TpwWav.rst
new file mode 100644
index 00000000000000..db3d637248ec1d
--- /dev/null
+++ b/Misc/NEWS.d/next/Tests/2023-09-05-20-46-35.gh-issue-108927.TpwWav.rst
@@ -0,0 +1,2 @@
+Fixed failure for tests running sequentially in the same process when
+test_importlib occurs between two other tests that use test_importlib.util.

From e52be9bbbbc57a4bc9b2c6079807feab8004bbc7 Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Tue, 5 Sep 2023 21:27:07 +0300
Subject: [PATCH 02/13] Update NEWS entry.

---
 .../Tests/2023-09-05-20-46-35.gh-issue-108927.TpwWav.rst    | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/Misc/NEWS.d/next/Tests/2023-09-05-20-46-35.gh-issue-108927.TpwWav.rst b/Misc/NEWS.d/next/Tests/2023-09-05-20-46-35.gh-issue-108927.TpwWav.rst
index db3d637248ec1d..760dff51cb031d 100644
--- a/Misc/NEWS.d/next/Tests/2023-09-05-20-46-35.gh-issue-108927.TpwWav.rst
+++ b/Misc/NEWS.d/next/Tests/2023-09-05-20-46-35.gh-issue-108927.TpwWav.rst
@@ -1,2 +1,4 @@
-Fixed failure for tests running sequentially in the same process when
-test_importlib occurs between two other tests that use test_importlib.util.
+Fixed order dendence in running tests in the same process
+when a test that has submodules (e.g. test_importlib) follows a test that
+imports its submodule (e.g. test_importlib.util) and precedes a test
+(e.g. test_unittest or test_compileall) that uses that submodule.

From 68c014e1df5d813580e8040ac11ed3c3442b13ee Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Wed, 6 Sep 2023 11:02:02 +0300
Subject: [PATCH 03/13] Fix unloading the newly imported modules after testing.

---
 Lib/test/libregrtest/main.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/Lib/test/libregrtest/main.py b/Lib/test/libregrtest/main.py
index ab03647ca5802f..1bff1522c9f4a3 100644
--- a/Lib/test/libregrtest/main.py
+++ b/Lib/test/libregrtest/main.py
@@ -463,9 +463,9 @@ def run_test(self, test_index, test_name, previous_test, save_modules):
             self.accumulate_result(result)
 
         # Unload the newly imported modules (best effort finalization)
-        for module in sys.modules.keys():
+        for module in list(sys.modules):
             if module not in save_modules and module.startswith("test."):
-                support.unload(module)
+                sys.modules.pop(module, None)
 
         return result
 
@@ -480,7 +480,7 @@ def run_tests_sequentially(self, runtests):
             import trace
             self.tracer = trace.Trace(trace=False, count=True)
 
-        save_modules = sys.modules.keys()
+        save_modules = set(sys.modules)
 
         msg = "Run tests sequentially"
         if timeout:

From 3f25ab447a52d9102c3004666366878adf97cd7f Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Tue, 12 Sep 2023 11:51:48 +0300
Subject: [PATCH 04/13] Add tests.

---
 .../regrtestdata/import_from_tests/test_regrtest_a.py     | 6 ++++++
 .../import_from_tests/test_regrtest_b/__init__.py         | 5 +++++
 .../import_from_tests/test_regrtest_b/util.py             | 0
 .../regrtestdata/import_from_tests/test_regrtest_c.py     | 6 ++++++
 Lib/test/test_regrtest.py                                 | 8 ++++++++
 5 files changed, 25 insertions(+)
 create mode 100644 Lib/test/regrtestdata/import_from_tests/test_regrtest_a.py
 create mode 100644 Lib/test/regrtestdata/import_from_tests/test_regrtest_b/__init__.py
 create mode 100644 Lib/test/regrtestdata/import_from_tests/test_regrtest_b/util.py
 create mode 100644 Lib/test/regrtestdata/import_from_tests/test_regrtest_c.py

diff --git a/Lib/test/regrtestdata/import_from_tests/test_regrtest_a.py b/Lib/test/regrtestdata/import_from_tests/test_regrtest_a.py
new file mode 100644
index 00000000000000..f225e21bad2e76
--- /dev/null
+++ b/Lib/test/regrtestdata/import_from_tests/test_regrtest_a.py
@@ -0,0 +1,6 @@
+import unittest
+import test_regrtest_b.util
+
+class Test(unittest.TestCase):
+    def test(self):
+        test_regrtest_b.util
diff --git a/Lib/test/regrtestdata/import_from_tests/test_regrtest_b/__init__.py b/Lib/test/regrtestdata/import_from_tests/test_regrtest_b/__init__.py
new file mode 100644
index 00000000000000..feb9d9781a8225
--- /dev/null
+++ b/Lib/test/regrtestdata/import_from_tests/test_regrtest_b/__init__.py
@@ -0,0 +1,5 @@
+import unittest
+
+class Test(unittest.TestCase):
+    def test(self):
+        pass
diff --git a/Lib/test/regrtestdata/import_from_tests/test_regrtest_b/util.py b/Lib/test/regrtestdata/import_from_tests/test_regrtest_b/util.py
new file mode 100644
index 00000000000000..e69de29bb2d1d6
diff --git a/Lib/test/regrtestdata/import_from_tests/test_regrtest_c.py b/Lib/test/regrtestdata/import_from_tests/test_regrtest_c.py
new file mode 100644
index 00000000000000..f225e21bad2e76
--- /dev/null
+++ b/Lib/test/regrtestdata/import_from_tests/test_regrtest_c.py
@@ -0,0 +1,6 @@
+import unittest
+import test_regrtest_b.util
+
+class Test(unittest.TestCase):
+    def test(self):
+        test_regrtest_b.util
diff --git a/Lib/test/test_regrtest.py b/Lib/test/test_regrtest.py
index 7cf3d05a6e6d70..c76e17a7cfd6e9 100644
--- a/Lib/test/test_regrtest.py
+++ b/Lib/test/test_regrtest.py
@@ -1866,6 +1866,14 @@ def test_random_seed(self):
     def test_random_seed_workers(self):
         self._check_random_seed(run_workers=True)
 
+    def test_import_from_tests(self):
+        testdir = os.path.join(os.path.dirname(__file__),
+                               'regrtestdata', 'import_from_tests')
+        tests = [f'test_regrtest_{name}' for name in ('a', 'b', 'c')]
+        args = ['-Wd', '-E', '-bb', '-m', 'test', '--testdir=%s' % testdir, *tests]
+        output = self.run_python(args)
+        self.check_executed_tests(output, tests, stats=3)
+
 
 class TestUtils(unittest.TestCase):
     def test_format_duration(self):

From 76732484f08d0a44592f8c7e34a2dea65083f774 Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Tue, 12 Sep 2023 23:32:03 +0300
Subject: [PATCH 05/13] Update
 Misc/NEWS.d/next/Tests/2023-09-05-20-46-35.gh-issue-108927.TpwWav.rst

Co-authored-by: Brett Cannon <brett@python.org>
---
 .../next/Tests/2023-09-05-20-46-35.gh-issue-108927.TpwWav.rst   | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Misc/NEWS.d/next/Tests/2023-09-05-20-46-35.gh-issue-108927.TpwWav.rst b/Misc/NEWS.d/next/Tests/2023-09-05-20-46-35.gh-issue-108927.TpwWav.rst
index 760dff51cb031d..b1a78370afedb2 100644
--- a/Misc/NEWS.d/next/Tests/2023-09-05-20-46-35.gh-issue-108927.TpwWav.rst
+++ b/Misc/NEWS.d/next/Tests/2023-09-05-20-46-35.gh-issue-108927.TpwWav.rst
@@ -1,4 +1,4 @@
-Fixed order dendence in running tests in the same process
+Fixed order dependence in running tests in the same process
 when a test that has submodules (e.g. test_importlib) follows a test that
 imports its submodule (e.g. test_importlib.util) and precedes a test
 (e.g. test_unittest or test_compileall) that uses that submodule.

From 5df4c8b0b7b3d502cf244a52ab97e1966f38d6c4 Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Wed, 13 Sep 2023 10:55:46 +0300
Subject: [PATCH 06/13] Move save/unload modules down in single.py.

---
 Lib/test/libregrtest/main.py     |  7 -------
 Lib/test/libregrtest/save_env.py | 12 ++++++++++++
 Lib/test/libregrtest/single.py   |  7 ++++---
 3 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/Lib/test/libregrtest/main.py b/Lib/test/libregrtest/main.py
index 5e4f5739d3a4f1..5cb43b963dadfa 100644
--- a/Lib/test/libregrtest/main.py
+++ b/Lib/test/libregrtest/main.py
@@ -293,8 +293,6 @@ def run_tests_sequentially(self, runtests):
         else:
             tracer = None
 
-        save_modules = set(sys.modules)
-
         jobs = runtests.get_jobs()
         if jobs is not None:
             tests = f'{jobs} tests'
@@ -317,11 +315,6 @@ def run_tests_sequentially(self, runtests):
 
             result = self.run_test(test_name, runtests, tracer)
 
-            # Unload the newly imported modules (best effort finalization)
-            for module in list(sys.modules):
-                if module not in save_modules and module.startswith("test."):
-                    sys.modules.pop(module, None)
-
             if result.must_stop(self.fail_fast, self.fail_env_changed):
                 break
 
diff --git a/Lib/test/libregrtest/save_env.py b/Lib/test/libregrtest/save_env.py
index b2cc381344b2ef..8b2d149d29f963 100644
--- a/Lib/test/libregrtest/save_env.py
+++ b/Lib/test/libregrtest/save_env.py
@@ -329,3 +329,15 @@ def __exit__(self, exc_type, exc_val, exc_tb):
                         f"  Before: {original}\n"
                         f"  After:  {current} ")
         return False
+
+
+class saved_sys_modules:
+
+    def __enter__(self):
+        self.save_modules = set(sys.modules)
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        # Unload the newly imported modules (best effort finalization)
+        for module in list(sys.modules):
+            if module not in self.save_modules and module.startswith("test."):
+                sys.modules.pop(module, None)
diff --git a/Lib/test/libregrtest/single.py b/Lib/test/libregrtest/single.py
index d491ffb9cd9aa2..b3a504aeee379f 100644
--- a/Lib/test/libregrtest/single.py
+++ b/Lib/test/libregrtest/single.py
@@ -14,7 +14,7 @@
 
 from .result import State, TestResult
 from .runtests import RunTests
-from .save_env import saved_test_environment
+from .save_env import saved_test_environment, saved_sys_modules
 from .setup import setup_tests
 from .utils import (
     TestName,
@@ -127,8 +127,9 @@ def _runtest_env_changed_exc(result: TestResult, runtests: RunTests,
         clear_caches()
         support.gc_collect()
 
-        with saved_test_environment(test_name,
-                                    runtests.verbose, quiet, pgo=pgo):
+        with (saved_sys_modules(),
+              saved_test_environment(test_name,
+                                    runtests.verbose, quiet, pgo=pgo)):
             _load_run_test(result, runtests)
     except support.ResourceDenied as msg:
         if not quiet and not pgo:

From 0eae53539c49a75cb00696b28c541b022ca1d599 Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Wed, 13 Sep 2023 13:26:34 +0300
Subject: [PATCH 07/13] Refactoring.

---
 Lib/test/libregrtest/save_env.py | 9 +++++----
 Lib/test/libregrtest/single.py   | 4 ++--
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/Lib/test/libregrtest/save_env.py b/Lib/test/libregrtest/save_env.py
index 8b2d149d29f963..25d16633e00881 100644
--- a/Lib/test/libregrtest/save_env.py
+++ b/Lib/test/libregrtest/save_env.py
@@ -331,13 +331,14 @@ def __exit__(self, exc_type, exc_val, exc_tb):
         return False
 
 
-class saved_sys_modules:
+class saved_test_modules:
 
     def __enter__(self):
         self.save_modules = set(sys.modules)
 
     def __exit__(self, exc_type, exc_val, exc_tb):
         # Unload the newly imported modules (best effort finalization)
-        for module in list(sys.modules):
-            if module not in self.save_modules and module.startswith("test."):
-                sys.modules.pop(module, None)
+        new_modules = [module for module in sys.modules
+                       if module not in self.save_modules and module.startswith("test.")]
+        for module in new_modules:
+            sys.modules.pop(module, None)
diff --git a/Lib/test/libregrtest/single.py b/Lib/test/libregrtest/single.py
index b3a504aeee379f..5c54419cfa6626 100644
--- a/Lib/test/libregrtest/single.py
+++ b/Lib/test/libregrtest/single.py
@@ -14,7 +14,7 @@
 
 from .result import State, TestResult
 from .runtests import RunTests
-from .save_env import saved_test_environment, saved_sys_modules
+from .save_env import saved_test_environment, saved_test_modules
 from .setup import setup_tests
 from .utils import (
     TestName,
@@ -127,7 +127,7 @@ def _runtest_env_changed_exc(result: TestResult, runtests: RunTests,
         clear_caches()
         support.gc_collect()
 
-        with (saved_sys_modules(),
+        with (saved_test_modules(),
               saved_test_environment(test_name,
                                     runtests.verbose, quiet, pgo=pgo)):
             _load_run_test(result, runtests)

From 66437b50b93bfd2fd60e96e7011a44131772ea0a Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Wed, 13 Sep 2023 15:29:13 +0300
Subject: [PATCH 08/13] Remove also attributes from parent modules.

---
 Lib/test/libregrtest/save_env.py | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/Lib/test/libregrtest/save_env.py b/Lib/test/libregrtest/save_env.py
index 25d16633e00881..9a5db51d6624a2 100644
--- a/Lib/test/libregrtest/save_env.py
+++ b/Lib/test/libregrtest/save_env.py
@@ -339,6 +339,13 @@ def __enter__(self):
     def __exit__(self, exc_type, exc_val, exc_tb):
         # Unload the newly imported modules (best effort finalization)
         new_modules = [module for module in sys.modules
-                       if module not in self.save_modules and module.startswith("test.")]
+                       if module not in self.save_modules and
+                          module.startswith("test.")]
         for module in new_modules:
             sys.modules.pop(module, None)
+            # Remove the attribute of the parent module.
+            parent, _, name = module.rpartition('.')
+            try:
+                delattr(sys.modules[parent], name)
+            except (KeyError, AttributeError):
+                pass

From 56621abe6c06ea57bc2bdca360eea2d6fb4f70b1 Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Tue, 28 Nov 2023 16:01:33 +0200
Subject: [PATCH 09/13] Only unload modules if run tests sequentially.

---
 Lib/test/libregrtest/main.py     | 15 +++++++++++++++
 Lib/test/libregrtest/save_env.py | 20 --------------------
 Lib/test/libregrtest/single.py   |  7 +++----
 3 files changed, 18 insertions(+), 24 deletions(-)

diff --git a/Lib/test/libregrtest/main.py b/Lib/test/libregrtest/main.py
index 5420247f9ad0e0..69ab66272a9609 100644
--- a/Lib/test/libregrtest/main.py
+++ b/Lib/test/libregrtest/main.py
@@ -309,6 +309,8 @@ def run_tests_sequentially(self, runtests) -> None:
         else:
             tracer = None
 
+        save_modules = set(sys.modules)
+
         jobs = runtests.get_jobs()
         if jobs is not None:
             tests = count(jobs, 'test')
@@ -331,6 +333,19 @@ def run_tests_sequentially(self, runtests) -> None:
 
             result = self.run_test(test_name, runtests, tracer)
 
+            # Unload the newly imported modules (best effort finalization)
+            new_modules = [module for module in sys.modules
+                           if module not in save_modules and
+                                module.startswith("test.")]
+            for module in new_modules:
+                sys.modules.pop(module, None)
+                # Remove the attribute of the parent module.
+                parent, _, name = module.rpartition('.')
+                try:
+                    delattr(sys.modules[parent], name)
+                except (KeyError, AttributeError):
+                    pass
+
             if result.must_stop(self.fail_fast, self.fail_env_changed):
                 break
 
diff --git a/Lib/test/libregrtest/save_env.py b/Lib/test/libregrtest/save_env.py
index 9a5db51d6624a2..b2cc381344b2ef 100644
--- a/Lib/test/libregrtest/save_env.py
+++ b/Lib/test/libregrtest/save_env.py
@@ -329,23 +329,3 @@ def __exit__(self, exc_type, exc_val, exc_tb):
                         f"  Before: {original}\n"
                         f"  After:  {current} ")
         return False
-
-
-class saved_test_modules:
-
-    def __enter__(self):
-        self.save_modules = set(sys.modules)
-
-    def __exit__(self, exc_type, exc_val, exc_tb):
-        # Unload the newly imported modules (best effort finalization)
-        new_modules = [module for module in sys.modules
-                       if module not in self.save_modules and
-                          module.startswith("test.")]
-        for module in new_modules:
-            sys.modules.pop(module, None)
-            # Remove the attribute of the parent module.
-            parent, _, name = module.rpartition('.')
-            try:
-                delattr(sys.modules[parent], name)
-            except (KeyError, AttributeError):
-                pass
diff --git a/Lib/test/libregrtest/single.py b/Lib/test/libregrtest/single.py
index 0851f30feef253..47368eb6ac7a06 100644
--- a/Lib/test/libregrtest/single.py
+++ b/Lib/test/libregrtest/single.py
@@ -13,7 +13,7 @@
 from .filter import match_test
 from .result import State, TestResult, TestStats
 from .runtests import RunTests
-from .save_env import saved_test_environment, saved_test_modules
+from .save_env import saved_test_environment
 from .setup import setup_tests
 from .testresult import get_test_runner
 from .utils import (
@@ -173,9 +173,8 @@ def _runtest_env_changed_exc(result: TestResult, runtests: RunTests,
         clear_caches()
         support.gc_collect()
 
-        with (saved_test_modules(),
-              saved_test_environment(test_name,
-                                    runtests.verbose, quiet, pgo=pgo)):
+        with saved_test_environment(test_name,
+                                    runtests.verbose, quiet, pgo=pgo):
             _load_run_test(result, runtests)
     except support.ResourceDenied as exc:
         if not quiet and not pgo:

From ba5597afa6935cece477d54553c7e859ec61fec3 Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Fri, 1 Dec 2023 11:15:11 +0200
Subject: [PATCH 10/13] Apply suggestions from code review

Co-authored-by: Victor Stinner <vstinner@python.org>
---
 Lib/test/libregrtest/main.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Lib/test/libregrtest/main.py b/Lib/test/libregrtest/main.py
index 69ab66272a9609..68f1882b316f9f 100644
--- a/Lib/test/libregrtest/main.py
+++ b/Lib/test/libregrtest/main.py
@@ -333,7 +333,7 @@ def run_tests_sequentially(self, runtests) -> None:
 
             result = self.run_test(test_name, runtests, tracer)
 
-            # Unload the newly imported modules (best effort finalization)
+            # Unload the newly imported test modules (best effort finalization)
             new_modules = [module for module in sys.modules
                            if module not in save_modules and
                                 module.startswith("test.")]

From 1aae3412f7fd102525c2ae7ca88b7b196316220a Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Mon, 4 Dec 2023 12:57:15 +0200
Subject: [PATCH 11/13] Add a comment.

---
 Lib/test/test_regrtest.py | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/Lib/test/test_regrtest.py b/Lib/test/test_regrtest.py
index c2a97ec6341027..982f8393cba415 100644
--- a/Lib/test/test_regrtest.py
+++ b/Lib/test/test_regrtest.py
@@ -2032,6 +2032,17 @@ def test_dev_mode(self):
                                   stats=len(tests), parallel=True)
 
     def test_import_from_tests(self):
+        # Test that unloading test modules does not break tests
+        # that import from other tests.
+        # The test execution order matters for this test.
+        # Both test_regrtest_a and test_regrtest_c which are executed before
+        # and after test_regrtest_b import a submodule from the test_regrtest_b
+        # package and use it in testing. test_regrtest_b itself does not import
+        # that submodule.
+        # Previously test_regrtest_c failed because test_regrtest_b.util in
+        # sys.modules was left after test_regrtest_a (making the import
+        # statement no-op), but new test_regrtest_b without the util attribute
+        # was imported for test_regrtest_b.
         testdir = os.path.join(os.path.dirname(__file__),
                                'regrtestdata', 'import_from_tests')
         tests = [f'test_regrtest_{name}' for name in ('a', 'b', 'c')]

From 017f01de9deadc34fd05f1c818e127da3b1a2f86 Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Mon, 4 Dec 2023 12:57:43 +0200
Subject: [PATCH 12/13] Test that test modules are really unloaded.

---
 Lib/test/libregrtest/main.py                               | 2 +-
 Lib/test/regrtestdata/import_from_tests/test_regrtest_a.py | 7 ++++++-
 .../import_from_tests/test_regrtest_b/__init__.py          | 6 +++++-
 Lib/test/regrtestdata/import_from_tests/test_regrtest_c.py | 7 ++++++-
 4 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/Lib/test/libregrtest/main.py b/Lib/test/libregrtest/main.py
index c6cc70618193e1..8bb66f662477b0 100644
--- a/Lib/test/libregrtest/main.py
+++ b/Lib/test/libregrtest/main.py
@@ -338,7 +338,7 @@ def run_tests_sequentially(self, runtests) -> None:
             # Unload the newly imported modules (best effort finalization)
             new_modules = [module for module in sys.modules
                            if module not in save_modules and
-                                module.startswith("test.")]
+                                module.startswith(("test.", "test_"))]
             for module in new_modules:
                 sys.modules.pop(module, None)
                 # Remove the attribute of the parent module.
diff --git a/Lib/test/regrtestdata/import_from_tests/test_regrtest_a.py b/Lib/test/regrtestdata/import_from_tests/test_regrtest_a.py
index f225e21bad2e76..9c3d0c7cf4bfaa 100644
--- a/Lib/test/regrtestdata/import_from_tests/test_regrtest_a.py
+++ b/Lib/test/regrtestdata/import_from_tests/test_regrtest_a.py
@@ -1,6 +1,11 @@
+import sys
 import unittest
 import test_regrtest_b.util
 
 class Test(unittest.TestCase):
     def test(self):
-        test_regrtest_b.util
+        test_regrtest_b.util  # does not fail
+        self.assertIn('test_regrtest_a', sys.modules)
+        self.assertIs(sys.modules['test_regrtest_b'], test_regrtest_b)
+        self.assertIs(sys.modules['test_regrtest_b.util'], test_regrtest_b.util)
+        self.assertNotIn('test_regrtest_c', sys.modules)
diff --git a/Lib/test/regrtestdata/import_from_tests/test_regrtest_b/__init__.py b/Lib/test/regrtestdata/import_from_tests/test_regrtest_b/__init__.py
index feb9d9781a8225..3dfba253455ad2 100644
--- a/Lib/test/regrtestdata/import_from_tests/test_regrtest_b/__init__.py
+++ b/Lib/test/regrtestdata/import_from_tests/test_regrtest_b/__init__.py
@@ -1,5 +1,9 @@
+import sys
 import unittest
 
 class Test(unittest.TestCase):
     def test(self):
-        pass
+        self.assertNotIn('test_regrtest_a', sys.modules)
+        self.assertIn('test_regrtest_b', sys.modules)
+        self.assertNotIn('test_regrtest_b.util', sys.modules)
+        self.assertNotIn('test_regrtest_c', sys.modules)
diff --git a/Lib/test/regrtestdata/import_from_tests/test_regrtest_c.py b/Lib/test/regrtestdata/import_from_tests/test_regrtest_c.py
index f225e21bad2e76..de80769118d709 100644
--- a/Lib/test/regrtestdata/import_from_tests/test_regrtest_c.py
+++ b/Lib/test/regrtestdata/import_from_tests/test_regrtest_c.py
@@ -1,6 +1,11 @@
+import sys
 import unittest
 import test_regrtest_b.util
 
 class Test(unittest.TestCase):
     def test(self):
-        test_regrtest_b.util
+        test_regrtest_b.util  # does not fail
+        self.assertNotIn('test_regrtest_a', sys.modules)
+        self.assertIs(sys.modules['test_regrtest_b'], test_regrtest_b)
+        self.assertIs(sys.modules['test_regrtest_b.util'], test_regrtest_b.util)
+        self.assertIn('test_regrtest_c', sys.modules)

From b3ea8faa682450998b5a912ad44d7a6f4b998027 Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Mon, 4 Dec 2023 17:08:07 +0200
Subject: [PATCH 13/13] Update Lib/test/test_regrtest.py

Co-authored-by: Victor Stinner <vstinner@python.org>
---
 Lib/test/test_regrtest.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Lib/test/test_regrtest.py b/Lib/test/test_regrtest.py
index 982f8393cba415..e828941f6c779d 100644
--- a/Lib/test/test_regrtest.py
+++ b/Lib/test/test_regrtest.py
@@ -2031,7 +2031,7 @@ def test_dev_mode(self):
         self.check_executed_tests(output, tests,
                                   stats=len(tests), parallel=True)
 
-    def test_import_from_tests(self):
+    def test_unload_tests(self):
         # Test that unloading test modules does not break tests
         # that import from other tests.
         # The test execution order matters for this test.