docs: regression testing protocol for live migration verification

[joshua-quek-sonarsource]

Summary

• Adds docs/regression-testing.md — a reusable 7-phase protocol for verifying features/fixes against a live SQ→SC migration
• Designed as a prompt for AI coding agents to follow after implementation
• Includes Angular Framework test environment reference and a worked example (parallel issue sync)

Test plan

• Verified no secrets leaked in docs (grep for tokens, staging URLs are not secrets)
• Doc is self-contained and actionable

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[sonar-review-alpha]

Summary

This PR adds a comprehensive 7-phase regression testing protocol (docs/regression-testing.md) designed as an AI agent prompt for verifying features and fixes against a live SonarQube→SonarCloud migration. The protocol covers adversarial code review, environment setup, test execution, result analysis, investigation, and remediation. It includes a reference section for the Angular Framework test environment (38K+ issues, 400+ hotspots) and practical scripts for generating test data. Grounded in real experience: a worked example demonstrates the protocol successfully caught silent API failures and guided a fix that improved sync success rates from 14% to 99%+.

What reviewers should know

What to verify:

• Phase clarity: Each of the 7 phases should be specific enough that an AI agent (or human) can follow it mechanically without judgment calls. Spot-check phases 4 and 5 — they're the most complex and hardest to execute consistently.
• Worked example credibility: The final example (parallel issue sync) demonstrates that the protocol caught real bugs (silent API failures in catch blocks) and guided a concrete fix. The before/after stats (0% → 99%+ success) validate that the protocol is thorough.
• Actionability: The reference section (SQ/SC URLs, project keys) and the bulk-tagging Python script should make it easy to set up test conditions. Check that script syntax is correct and the SQ API calls match the API version in use.
• Scope: This is pure documentation — no code changes, no breaking changes, no risk of regression. The protocol is advisory (a prompt to be given to agents), not enforced.

Why this matters: Live migration testing is error-prone and easy to skip. This protocol makes it systematic and repeatable. The worked example proves it catches bugs that would otherwise ship.

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🗣️ Give feedback

[sonar-review-alpha]

LGTM! ✅

Documentation-only PR, nothing to block merge. The protocol is internally consistent and the worked example grounds it in real test results.

🗣️ Give feedback

[joshua-quek-sonarsource]

Hi @joe-tingsanchali-sonarsource - I will merge this in soon.
@okorach-sonar and I are doing some testing.