https://coverage.readthedocs.io/en/stable/config.html

- Enable the required parallel mode
- Set the required `COVERAGE_PROCESS_START` environment variable
- Add `coverage_enable_subprocess` for `coverage.process_startup`
- Combine coverage reports before reporting coverage
- Update `.gitignore` to ignore files named `.coverage*`

https://coverage.readthedocs.io/en/latest/subprocess.html

Occasional flakes are seen with some less-common signals.
This commit will add some simple conditionals to avoid `AssertionError`
exceptions when those signals are not handled as expected.

`WatchFilesReload` flakes when used with coverage.py parallel mode.
It may have to do with the threading in the `touch_soon` fixture.

Other WatchGod and Watchfiles flake on Windows specifically. Errors:

```text
================================== FAILURES ===================================
___________ TestBaseReload.test_override_defaults[WatchFilesReload] ___________

self = <test_reload.TestBaseReload object at 0x0000014D4AB94160>
touch_soon = <function touch_soon.<locals>.start at 0x0000014D4C3192D0>

    @pytest.mark.parametrize("reloader_class", [WatchFilesReload, WatchGodReload])
    def test_override_defaults(self, touch_soon) -> None:
        dotted_file = self.reload_path / ".dotted"
        dotted_dir_file = self.reload_path / ".dotted_dir" / "file.txt"
        python_file = self.reload_path / "main.py"

        with as_cwd(self.reload_path):
            config = Config(
                app="tests.test_config:asgi_app",
                reload=True,
                # We need to add *.txt otherwise no regular files will match
                reload_includes=[".*", "*.txt"],
                reload_excludes=["*.py"],
            )
            reloader = self._setup_reloader(config)

            assert self._reload_tester(touch_soon, reloader, dotted_file)
            assert self._reload_tester(touch_soon, reloader, dotted_dir_file)
>           assert not self._reload_tester(touch_soon, reloader, python_file)
E           AssertionError: assert not [WindowsPath('C:/Users/runneradmin/AppData/Local/Temp/pytest-of-runneradmin/pytest-0/reload_directory1/.coverage.fv-az811-309.2664.795750')]
E            +  where [WindowsPath('C:/Users/runneradmin/AppData/Local/Temp/pytest-of-runneradmin/pytest-0/reload_directory1/.coverage.fv-az811-309.2664.795750')] = <bound method TestBaseReload._reload_tester of <test_reload.TestBaseReload object at 0x0000014D4AB94160>>(<function touch_soon.<locals>.start at 0x0000014D4C3192D0>, <uvicorn.supervisors.watchfilesreload.WatchFilesReload object at 0x0000014D4C39DEA0>, WindowsPath('C:/Users/runneradmin/AppData/Local/Temp/pytest-of-runneradmin/pytest-0/reload_directory1/main.py'))
E            +    where <bound method TestBaseReload._reload_tester of <test_reload.TestBaseReload object at 0x0000014D4AB94160>> = <test_reload.TestBaseReload object at 0x0000014D4AB94160>._reload_tester

tests\supervisors\test_reload.py:253: AssertionError
---------------------------- Captured stderr call -----------------------------
INFO:     Will watch for changes in these directories: ['C:\\Users\\runneradmin\\AppData\\Local\\Temp\\pytest-of-runneradmin\\pytest-0\\reload_directory1']
INFO:     Started reloader process [6280] using WatchFiles
------------------------------ Captured log call ------------------------------
INFO     uvicorn.error:config.py:345 Will watch for changes in these directories: ['C:\\Users\\runneradmin\\AppData\\Local\\Temp\\pytest-of-runneradmin\\pytest-0\\reload_directory1']
INFO     uvicorn.error:basereload.py:77 Started reloader process [6280] using WatchFiles
____________ TestBaseReload.test_override_defaults[WatchGodReload] ____________

self = <test_reload.TestBaseReload object at 0x0000014D4AB959F0>
touch_soon = <function touch_soon.<locals>.start at 0x0000014D4C3E77F0>

    @pytest.mark.parametrize("reloader_class", [WatchFilesReload, WatchGodReload])
    def test_override_defaults(self, touch_soon) -> None:
        dotted_file = self.reload_path / ".dotted"
        dotted_dir_file = self.reload_path / ".dotted_dir" / "file.txt"
        python_file = self.reload_path / "main.py"

        with as_cwd(self.reload_path):
            config = Config(
                app="tests.test_config:asgi_app",
                reload=True,
                # We need to add *.txt otherwise no regular files will match
                reload_includes=[".*", "*.txt"],
                reload_excludes=["*.py"],
            )
            reloader = self._setup_reloader(config)

            assert self._reload_tester(touch_soon, reloader, dotted_file)
>           assert self._reload_tester(touch_soon, reloader, dotted_dir_file)

tests\supervisors\test_reload.py:252:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <test_reload.TestBaseReload object at 0x0000014D4AB959F0>
touch_soon = <function touch_soon.<locals>.start at 0x0000014D4C3E77F0>
reloader = <uvicorn.supervisors.watchgodreload.WatchGodReload object at 0x0000014D4C39DAB0>
files = (WindowsPath('C:/Users/runneradmin/AppData/Local/Temp/pytest-of-runneradmin/pytest-0/reload_directory1/.dotted_dir/file.txt'),)
@py_assert2 = [WindowsPath('C:/Users/runneradmin/AppData/Local/Temp/pytest-of-runneradmin/pytest-0/reload_directory1/.coverage.fv-az...s/runneradmin/AppData/Local/Temp/pytest-of-runneradmin/pytest-0/reload_directory1/.coverage.fv-az811-309.4856.060689')]
@py_assert4 = False
@py_format5 = "assert not [WindowsPath('C:/Users/runneradmin/AppData/Local/Temp/pytest-of-runneradmin/pytest-0/reload_directory1/.co...v-az811-309.4856.060689')] = next(<uvicorn.supervisors.watchgodreload.WatchGodReload object at 0x0000014D4C39DAB0>)\n}"

    def _reload_tester(
        self, touch_soon, reloader: BaseReload, *files: Path
    ) -> Optional[List[Path]]:
        reloader.restart()
        if WatchFilesReload is not None and isinstance(reloader, WatchFilesReload):
            touch_soon(*files)
        else:
>           assert not next(reloader)
E           AssertionError: assert not [WindowsPath('C:/Users/runneradmin/AppData/Local/Temp/pytest-of-runneradmin/pytest-0/reload_directory1/.coverage.fv-az...s/runneradmin/AppData/Local/Temp/pytest-of-runneradmin/pytest-0/reload_directory1/.coverage.fv-az811-309.4856.060689')]
E            +  where [WindowsPath('C:/Users/runneradmin/AppData/Local/Temp/pytest-of-runneradmin/pytest-0/reload_directory1/.coverage.fv-az...s/runneradmin/AppData/Local/Temp/pytest-of-runneradmin/pytest-0/reload_directory1/.coverage.fv-az811-309.4856.060689')] = next(<uvicorn.supervisors.watchgodreload.WatchGodReload object at 0x0000014D4C39DAB0>)

tests\supervisors\test_reload.py:63: AssertionError
---------------------------- Captured stderr call -----------------------------
INFO:     Will watch for changes in these directories: ['C:\\Users\\runneradmin\\AppData\\Local\\Temp\\pytest-of-runneradmin\\pytest-0\\reload_directory1']
INFO:     Started reloader process [6280] using WatchGod
------------------------------ Captured log call ------------------------------
INFO     uvicorn.error:config.py:345 Will watch for changes in these directories: ['C:\\Users\\runneradmin\\AppData\\Local\\Temp\\pytest-of-runneradmin\\pytest-0\\reload_directory1']
INFO     uvicorn.error:basereload.py:77 Started reloader process [6280] using WatchGod
```

The GitHub Actions `jobs.<job_id>.strategy.fail-fast` setting controls
how failures are handled. The default of `true` will fail the entire job
when any job in the matrix fails.

With the introduction of platform-specific worker testing, subprocesses,
and operating system signal handling, there is potential for specific
workflow jobs to occasionally fail. In these cases, it can help to set
`fail-fast: false` to ensure that those specific failed jobs can be
identified.

https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions

With the introduction of platform-specific worker testing, subprocesses,
and operating system signal handling, there is potential for specific
workflow jobs to occasionally hang. In these cases, it can help to set
a timeout on the test step to ensure the workflow jobs don't hang until
the default 360 minute (6 hour) timeout.

https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions

- Explain how to skip subprocess tests by using the custom pytest marker
- Explain how to re-run failed GitHub Actions jobs

This reverts commit 1d472e2.

#1995 (comment)

#1995 (comment)

#1995 (comment)

Conflicts:
pyproject.toml
requirements.txt

https://coverage.readthedocs.io/en/latest/cmd.html#cmd-combine