Build Mutation Testing Configuration for Achieving 80% Mutation Score on Core Services

[temma02]

Description

Configure and tune mutation testing to achieve and enforce an 80% mutation score across the core service layer, identifying and closing gaps where existing tests fail to detect injected mutations.

Requirements and Context

• Testing: Configure Stryker for all core services in apps/backend/src/services/ and apps/frontend/src/services/
• Coverage: Achieve 80% mutation score on core services
• Documentation: Update docs/mutation-testing.md

Suggested Execution

Branch: test/issue-050-core-services-mutation-score-80

Implement Changes

• Configure stryker.conf.json to target the core service layer
• Run mutation testing and identify surviving mutants
• Add or strengthen tests to kill surviving mutants until 80% score is reached
• Update docs/mutation-testing.md with the achieved scores

Test and Commit

• Achieve at least 80% mutation score on core services
• All newly added tests must be meaningful (not just mutant-killing hacks)
• Update mutation-testing.md with final scores

Example Commit Message

test(mutation): achieve 80% mutation score on core services

- Configure Stryker for backend and frontend core services
- Add tests to kill surviving mutants
- Update mutation-testing.md with achieved scores

Guidelines

• Focus on meaningful test improvements, not gaming the score
• Document any intentionally ignored mutants with justification
• Run mutation testing incrementally to keep runtime manageable

[Grace-CODE-D]

@Grace-CODE-D has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

i would like to work on this issue

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Grace-CODE-D to this issue.

[drips-wave]

Congratulations, @Grace-CODE-D! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 2, 2026.

🧑‍💻 @Grace-CODE-D: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

Warning

When opening a PR, please link it to this issue to ensure it gets tracked accurately. Points are awarded when this issue is marked as completed by the maintainer.

🤠 Repo maintainers: Please keep an eye on the contributor's progress and review their work before the due date. You can manage this issue, including adjusting its complexity and points, here.

🌊 Happy Wave 🌊