Testing Strategy

Design and implement comprehensive testing strategies with modern techniques.

When to Use

• User asks to plan test suites or choose testing approaches
• Need to decide between property-based, visual regression, load testing, etc.
• Even if they just say "how should we test this" or "what testing approach should we use"

Strategy Decision Tree

What are you testing?
├── Business logic / algorithms → Property-Based Testing
│   └── Tool: Hypothesis (Python), fast-check (JS)
├── UI appearance / visual state → Visual Regression
│   └── Tool: Playwright screenshots, Percy, Chromatic
├── Performance under load → Load & Stress Testing
│   └── Tool: Locust (Python), k6 (JS), JMeter (Java)
├── Test suite quality itself → Mutation Testing
│   └── Tool: Mutmut (Python), Stryker (JS/Java/C#)
└── End-to-end user flows → E2E Testing
    └── Tool: Playwright, Cypress, Selenium

Strategy Reference

Language-Specific Tools

Quality Gates

Integrate testing into CI/CD:

• Check mutation score thresholds (>80% target)
• Monitor Core Web Vitals in load tests (LCP < 2.5s)
• Auto-quarantine flaky tests after 3 consecutive failures
• Fail build if coverage drops on new code

Gotchas

• Property-based tests need shrinking configuration — without it, counterexamples are huge and unhelpful.
• Visual regression tests are environment-sensitive — use fixed viewport sizes and font rendering settings.
• Load tests against production data need anonymization — never use real customer data.
• Mutation testing on legacy code produces many surviving mutants — start with a baseline and improve incrementally.
• Flaky E2E tests erode trust — quarantine them immediately and fix root cause before re-enabling.

Rationalizations

Red Flags

• Declining code coverage on new features
• Committing code with failing or bypassed tests
• Ignoring flaky tests instead of identifying and fixing the root cause
• Running all tests on every change instead of targeted test selection

References

• Testing Strategy Patterns - Comprehensive collection of testing patterns and strategies

Appendix: Deterministic Testdata Builders (absorbed from testdata-builders)

Keep tests concise with pure-function factories (makeEntity(overrides)), realistic defaults, seeded randomness, and builders updated on every schema change (CI fails otherwise). Patterns: references/builder-patterns.md; strategy: references/test-data-strategy.md.

See Also

• test-runner — Execute tests and diagnose failures
• nested-build-isolation — Isolate nested subprocess builds, tests, or coverage runners
• dogfood — Exploratory testing of web applications

Voice & Context

• Default: professional + blog
• Reference: voice-profiles skill for definitions and auto-detection.