upload-codescene-coverage: add act-based end-to-end workflow test

[coderabbitai]

Summary

Add an act-based end-to-end workflow test for .github/actions/upload-codescene-coverage.

The repository documents behavioural validation with act and pytest, and other actions use this pattern. This action has no .github/workflows/test-upload-codescene-coverage.yml workflow and no CodeScene reference under tests/workflows/.

Required change

Create a dedicated workflow test for the action. Run it with act from the existing pytest workflow-test infrastructure. Cover the check-mode behaviour, including the applicable and skipped pull-request contexts.

Rationale

Unit tests of shell snippets and manifest assertions do not validate GitHub Actions expression evaluation or the composite action lifecycle. An act test provides end-to-end validation of the workflow integration.

Affected areas

• .github/workflows/test-upload-codescene-coverage.yml
• tests/workflows/
• docs/behavioural-validation-of-github-actions-with-act-and-pytest.md, if the new test requires documentation updates

Acceptance criteria

• A dedicated workflow exercises upload-codescene-coverage through act.
• Pytest runs the workflow through the repository's established act test infrastructure.
• Tests cover an applicable check-mode run and a skipped stacked-pull-request run.
• The test does not require production CodeScene credentials or network-dependent CLI installation.
• The workflow test is documented where required.

References

• Pull request: Skip inapplicable CodeScene coverage checks and surface diagnostics (#395) #399
• Requesting comment: Skip inapplicable CodeScene coverage checks and surface diagnostics (#395) #399 (comment)
• Requested by: @leynos

[coderabbitai]

🔗 Related PRs

leynos/monotony#25 - Wire CodeScene coverage upload into CI [merged]
leynos/rstest-xfail#28 - Wire CodeScene coverage upload and ratchet [merged]
leynos/statelet#26 - Onboard main-branch CodeScene coverage upload [merged]
#350 - Wire CodeScene coverage upload and ratchet [merged]
leynos/pylint-pypy-shim#34 - Wire the CodeScene coverage upload into CI [merged]
leynos/episodic#182 - Wire CodeScene coverage upload via the shared actions [merged]
leynos/falcon-correlate#83 - Wire CodeScene coverage upload via the shared actions [merged]

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