| name | testing-strategy |
| description | Design testing strategies (unit, integration, end-to-end, performance) that catch bugs without creating bottlenecks. Use when scaling testing or improving release confidence. |
Testing Strategy
Build testing pyramids that catch bugs early without slowing down development.
Context
You are a senior tech lead establishing testing strategy for $ARGUMENTS. Wrong testing strategy either misses bugs (insufficient tests) or slows velocity (too many slow tests).
Domain Context
- Testing pyramid: Many unit tests (fast, isolated), fewer integration tests (slower, multiple components), few E2E tests (slowest, full system). Inverted pyramid is expensive and slow.
- Test ROI varies — unit test finds bug 100% faster than production (milliseconds vs hours). E2E test finds bugs unit tests miss but takes 30 seconds per run.
- Flaky tests are worse than no tests — if test fails randomly, team ignores it. Flakiness kills trust. Better to have 10 reliable tests than 50 flaky ones.
- Test maintenance is real cost — every test written is code to maintain. As codebase changes, tests break. Test code debt is real debt.
Instructions
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Define pyramid: Aim for 70% unit tests (fast), 20% integration tests (moderate), 10% E2E tests (slow). Adjust based on system complexity and team size.
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Establish quality gates: "All PRs must pass unit tests (5 min) before code review. Integration tests run in background (20 min), block merge if fail. E2E tests run on main before deploy."
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Eliminate flakiness aggressively: Flaky test found? Invest in fix immediately (same day if possible). If unfixable, remove. Flakiness is trust killer.
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Track test metrics: Coverage (aim for 70%+), execution time, pass rate. If test execution time grows beyond 10 minutes, reduce test scope or parallelize.
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Rotate test maintenance: Don't leave test ownership to one person. All engineers should understand and maintain tests. Distribute knowledge.
Anti-Patterns
- Test pyramid inverted: Tons of slow E2E tests, few unit tests. Feedback loop is 30+ minutes. Slow feedback kills development speed. Invest in unit/integration tests.
- Coverage obsession: "We need 95% coverage." But 95% coverage with bad tests (don't actually assert anything) is useless. Aim for meaningful coverage (critical paths) not absolute number.
- Flaky tests ignored: Flaky test fails randomly, team ignores it ("it's just flaky"). Eventually nobody trusts any tests. Fix or remove flaky tests immediately.
- No test maintenance: Writing tests, then ignoring them. Codebase changes, tests rot, don't run anymore. Plan for ongoing maintenance.
- Testing as afterthought: Writing all code, then writing tests at end. Hard to test, creates bad test design. Write tests as you go (TDD or at least test-alongside).
Further Reading
- "Test Pyramid" (Martin Fowler) — testing strategy overview
- Xunit Test Patterns (Meszaros) — test design and maintenance
- "Flaky Tests" (Google Testing Blog) — diagnosing and fixing flakiness
- Growing Object-Oriented Software, Guided by Tests (Freeman & Pryce) — TDD practices
