SRVOCF-822: Replace test mocks with stubs and extract shared test infrastructure

[twoGiants]

Summary

• 🧪 Replace the useCluster mock in list page tests with a shared useK8sWatchResourceStub that lets the real hook run, catching shape mismatches between the hook and its consumers
• 🧪 Replace the TestConsumer render pattern in useCluster.test.tsx with renderHook from @testing-library/react
• 🧪 Remove the FunctionTable mock from list page tests so the real table component is exercised
• 🔧 Extract shared test infrastructure into src/common/testing/: authFake (session auth helpers), constants, mswServer (default MSW handlers), functionsClientStub, and the K8s watch resource stub with fixture builders
• 🔧 Move FUNCTION_NAME_LABEL and REVISION_LABEL from useCluster.ts to types.ts so both production code and test stubs can reference them without circular imports
• 🐛 Remove stale COPY testing/ testing/ from Dockerfile (directory no longer exists)
• 📚 Update TESTING.md to reflect new MSW handler location

Relates to SRVOCF-822

Checklist

• Updated docs/ARCHITECTURE.md (if there are relevant changes to our layered architecture)

Additional Info

This is preparatory test refactoring for the namespace scoping feature (SRVOCF-822). The feature implementation will land in a follow-up PR once SRVOCF-979 merges.

The key motivation is twofold. First, the list page tests mocked useCluster entirely, hiding the hook's internals behind pre-computed return values. With the shared useK8sWatchResourceStub, tests set up raw K8s resource fixtures (Knative Services, Deployments) and let the real useCluster derive status, replicas, and URL. Type or field changes in the hook's return shape are now caught immediately instead of passing against a stale mock.

Second, this PR cleans up and streamlines a large chunk of the test suite, introducing testing conventions and a common testing library under src/common/testing/. This library is intended to grow with reusable test doubles and fixtures in future PRs. Not all tests are refactored here; the remaining test files will be migrated incrementally as related work touches them.

[openshift-ci-robot]

@twoGiants: This pull request references SRVOCF-822 which is a valid jira issue.

Warning: The referenced jira issue has an invalid target version for the target branch this PR targets: expected the story to target the "5.1.0" version, but no target version was set.

Details

In response to this:

Summary

• 🧪 Replace the useCluster mock in list page tests with a shared useK8sWatchResourceStub that lets the real hook run, catching shape mismatches between the hook and its consumers
• 🧪 Replace the TestConsumer render pattern in useCluster.test.tsx with renderHook from @testing-library/react
• 🧪 Remove the FunctionTable mock from list page tests so the real table component is exercised
• 🔧 Extract shared test infrastructure into src/common/testing/: authFake (session auth helpers), constants, mswServer (default MSW handlers), functionsClientStub, and the K8s watch resource stub with fixture builders
• 🔧 Move FUNCTION_NAME_LABEL and REVISION_LABEL from useCluster.ts to types.ts so both production code and test stubs can reference them without circular imports
• 🐛 Remove stale COPY testing/ testing/ from Dockerfile (directory no longer exists)
• 📚 Update TESTING.md to reflect new MSW handler location

Relates to SRVOCF-822

Checklist

• Updated docs/ARCHITECTURE.md (if there are relevant changes to our layered architecture)

Additional Info

This is preparatory test refactoring for the namespace scoping feature (SRVOCF-822). The feature implementation will land in a follow-up PR once SRVOCF-979 merges.

The key motivation is twofold. First, the list page tests mocked useCluster entirely, hiding the hook's internals behind pre-computed return values. With the shared useK8sWatchResourceStub, tests set up raw K8s resource fixtures (Knative Services, Deployments) and let the real useCluster derive status, replicas, and URL. Type or field changes in the hook's return shape are now caught immediately instead of passing against a stale mock.

Second, this PR cleans up and streamlines a large chunk of the test suite, introducing testing conventions and a common testing library under src/common/testing/. This library is intended to grow with reusable test doubles and fixtures in future PRs. Not all tests are refactored here; the remaining test files will be migrated incrementally as related work touches them.

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[Cragsmann]

looks good, few nit picks

[pmeida]

Bad rebase, I think you removed this change:

🐛 Remove stale COPY testing/ testing/ from Dockerfile (directory no longer exists)

[pmeida]

/lgtm
/approve

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: pmeida

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[openshift-ci]

@twoGiants: all tests passed!

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