test_regrtest creates temporary test files called test_regrtest_pid_xxx.py in Lib/test/. The problem is that some tests like test___all__ and test_zipfile haves test relying on the list of Lib/test/test_*.py.

When tests are run in parallel, test_regrtest can creates temporary test_regrtest_pid_xxx.py files, test_zipfile sees them, test_regrtest removes them, and then test_zipfiles fails.

The best would be to write these temporary files into a temporary directory, but I failed to fix Lib/test/regrtest.py to load tests from a different directory. In theory, Python 3 supports packages with files splitted into multiple directories, in practice it doesn't seem to work :-p

Maybe test_regrtest should use a test submodule like Lib/test/temp_regrtest/ ?

test_regrtest started to create temporary test_xxx.py files since issue #25220. (Other changes to test_regrtest: issues #18174, #22806, #25260, #25306,  #25369, #25373, #25694).

======================================================================
ERROR: test_all (test.test___all__.AllTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/haypo/prog/python/default/Lib/test/test___all__.py", line 102, in test_all
    with open(path, "rb") as f:
FileNotFoundError: [Errno 2] No such file or directory: '/home/haypo/prog/python/default/Lib/test/test_regrtest_25743_noop20.py'

----------------------------------------------------------------------

The directory with test files can be read-only. test_regrtest should use temporary directory.

> The directory with test files can be read-only.

test_regrtest skips tests which requires to write in Lib/test/ if the write fails.

        except PermissionError as exc:
            if not sysconfig.is_python_build():
                self.skipTest("cannot write %s: %s" % (path, exc))

> test_regrtest should use temporary directory.

Yes! That's the purpose of this issue!

But I was unable to find a technical solution to implement this. I need to try harder :-)

You say you couldn’t get the test package to be split into multiple directories. What did you try? As far as I can see, we need a way for test_regrtest to invoke the child process with some flag to say “add this extra directory to test.__path__”.

Another idea is to make a loader script that loads the “test” module, patches its __path__, and then runs test.__main__ or whatever as usual.

Oh ok, I found a bug in the setup_tests() function of libregrtest: issue #26538.

Attached patch fixes this issue, it requires the patch of the issue issue #26538.

Hum, test_doctest, test_zipfile and test_pyclbr fail if test is converted to a package (if Lib/test/__init__.py is removed).

Attached patch fixes test_zipfile.

I created the issue #26569 for test_pyclbr failure.

I created the issue #26641 for doctest (test_doctest).

New changeset f7ddd72b70ea by Victor Stinner in branch 'default':
Issue #26295: When using "python3 -m test --testdir=TESTDIR", regrtest doesn't
https://hg.python.org/cpython/rev/f7ddd72b70ea

New changeset c83349c129c9 by Victor Stinner in branch 'default':
Issue #26295: test_regrtest now uses a temporary directory
https://hg.python.org/cpython/rev/c83349c129c9

New changeset e29f12ed4444 by Victor Stinner in branch 'default':
Issue #26295: Fix test_regrtest.test_tools_buildbot_test()
https://hg.python.org/cpython/rev/e29f12ed4444

New changeset e47e00723e5d by Victor Stinner in branch 'default':
Issue #26295: Enhanc test_regrtest.test_tools_script_run_tests()
https://hg.python.org/cpython/rev/e47e00723e5d

Finally, I fixed the issue differently: test_regrtest now creates a temporary directory and uses --testdir command line parameter.

Before, using --testdir didn't work because regrtest always added "test." prefix to module names (ex: test_os => test.test_os). It isn't the case anymore when --testdir is used.

Buildbots are green, so I close the issue.