Collect subprocess coverage

tests/test_cli_invocation.py

@@ -150,7 +150,6 @@ def test_implicit_help(self, mocked_runner: MockedRunner) -> None:
         assert result.exception is None, report_traceback(result.exception)
         assert result.exit_code == 0
 
-    # TODO: Collect test coverage stats for this entry point invocation
     @requires_venv("Entry point test")
     def test_entry_point_help_raw(self) -> None:
         expected_entry_point = Path(sys.executable).parent / "venvstacks"
@@ -169,7 +168,6 @@ def test_entry_point_help_raw(self) -> None:
         assert result.returncode == 0
         assert result.stdout is not None
 
-    # TODO: Collect test coverage stats for this entry point invocation
     @requires_venv("Entry point test")
     def test_entry_point_help(self) -> None:
         expected_entry_point = Path(sys.executable).parent / "venvstacks"
@@ -188,6 +186,24 @@ def test_entry_point_help(self) -> None:
         assert result.returncode == 0
         assert result.stdout is not None
 
+    def test_module_execution(self) -> None:
+        # TODO: `coverage.py` isn't picking this up as executing `venvstacks/__main__.py`
+        #       (even an indirect invocation via the runpy module doesn't get detected)
+        command = [sys.executable, "-m", "venvstacks", "--help"]
+        result = run_python_command_unchecked(
+            command, stdout=subprocess.PIPE, stderr=subprocess.PIPE
+        )
+        if result.stdout is not None:
+            # Usage message should suggest indirect execution
+            assert "Usage: python -m venvstacks [" in result.stdout
+            # Top-level callback docstring is used as the overall CLI help text
+            cli_help = cli.handle_app_options.__doc__
+            assert cli_help is not None
+            assert cli_help.strip() in result.stdout
+        # Check operation result last to ensure test results are as informative as possible
+        assert result.returncode == 0
+        assert result.stdout is not None
+
 
 EXPECTED_USAGE_PREFIX = "Usage: python -m venvstacks "
 EXPECTED_SUBCOMMANDS = ["lock", "build", "local-export", "publish"]

tox.ini

@@ -10,6 +10,9 @@ labels =
      static = lint,typecheck
 
 [testenv]
+# Multi-env performance tweak based on https://hynek.me/articles/turbo-charge-tox/
+package = wheel
+wheel_build_env = .pkg
 groups = dev
 allowlist_externals = pytest
 passenv =
@@ -19,28 +22,24 @@ commands =
     pytest {posargs:-m "not slow"} tests/
 
 [testenv:coverage]
-groups = dev
+# Subprocess coverage based on https://hynek.me/articles/turbo-charge-tox/
 allowlist_externals = coverage
-passenv =
-    CI
-    VENVSTACKS_*
+set_env = COVERAGE_PROCESS_START={toxinidir}/pyproject.toml
+commands_pre = python -c 'import pathlib; pathlib.Path("{env_site_packages_dir}/cov.pth").write_text("import coverage; coverage.process_startup()")'
 commands =
     coverage run --parallel -m pytest {posargs} tests/
 
 [testenv:format]
-groups = dev
 allowlist_externals = ruff
 commands =
     ruff format {posargs} src/ tests/ misc/
 
 [testenv:lint]
-groups = dev
 allowlist_externals = ruff
 commands =
     ruff check --exclude 'tests/sample_project' {posargs} src/ tests/ misc/
 
 [testenv:typecheck]
-groups = dev
 allowlist_externals = mypy
 commands =
     mypy --strict --exclude 'tests/sample_project' {posargs} src/ tests/ misc/