Testing Strategy

Design a practical testing strategy that catches real bugs without slowing development.

Step 1: Understand What's Being Tested

Before recommending test types, clarify:

• What's the system? — API, UI, CLI, library, data pipeline, infrastructure?
• What are the critical paths? — The workflows where bugs cause the most damage.
• What's the current state? — Existing test suite, coverage, CI pipeline?
• What's the team's testing culture? — TDD, test-after, no tests at all?

Step 2: The Testing Pyramid

Apply the right test type at the right level:

         /  E2E  \           Few — expensive, slow, brittle
        /----------\
       / Integration \       Some — test boundaries and contracts
      /----------------\
     /    Unit Tests     \   Many — fast, cheap, isolated
    /--------------------\

Unit Tests

• What: Individual functions, methods, classes in isolation
• When: Pure logic, calculations, data transformations, state machines
• Skip when: The function is just glue code that calls other things
• Key principle: Test behavior, not implementation. If refactoring internals breaks tests, the tests are too coupled.

Integration Tests

• What: Components working together — API + database, service + queue, auth + middleware
• When: Boundaries between systems, database queries, external API calls
• Skip when: The integration is trivial (simple CRUD with an ORM)
• Key principle: Use real dependencies where feasible (testcontainers, in-memory DBs). Mocks at boundaries hide real bugs.

End-to-End Tests

• What: Full user workflows through the actual system
• When: Critical business flows — signup, checkout, payment, core feature
• Skip when: The workflow is already well-covered by integration tests
• Key principle: Keep the suite small and stable. Flaky E2E tests are worse than no E2E tests.

Step 3: What to Test (and What Not To)

Always test:

• Business logic and domain rules
• Error handling and edge cases
• Security-critical paths (auth, authorization, input validation)
• Data integrity (migrations, serialization/deserialization)
• Integration points with external services

Often skip:

• Simple getters/setters with no logic
• Framework-generated boilerplate
• UI layout and styling (unless critical to the product)
• Third-party library internals

Step 4: Test Quality Checklist

Good tests are:

• Fast — The full suite runs in under 5 minutes for unit tests
• Deterministic — No flaky tests. Same input = same result, every time.
• Independent — Tests don't depend on execution order or shared state
• Readable — Test names describe the scenario and expected outcome
• Maintainable — Refactoring production code doesn't require rewriting every test

Output

Produce a testing strategy document with:

1. Recommended test types for each component/layer
2. Critical paths that need coverage first
3. Suggested test tooling (framework, assertion library, mocking)
4. Coverage targets (with reasoning — 80% is not always the right answer)
5. CI integration recommendations (when to run which tests)