testing-anti-patterns

Testing mock behavior verifies only that mocks exist or function, not that your component works correctly. Test real behavior by asserting on component output, state changes, or side effects—not on mock call counts or arguments. This ensures tests catch actual bugs.

Incomplete mocks leave gaps between test assumptions and real dependencies, causing tests to pass in isolation but fail in production. Mock completely by understanding all dependency interactions, then verify your component handles real-world responses and edge cases consistently.

No. Test-only methods pollute production code, break encapsulation, and hide real behavior from actual users. Keep production classes clean by testing through public APIs and refactoring to expose necessary internals if needed for legitimate reasons.

Test what users see and experience—component output, UI state, accessibility features, and observable side effects—rather than internal logic or structure. This makes tests resilient to refactoring and catches actual breaks in functionality.

Never mock without understanding what dependencies do and why. Write tests against genuine behavior contracts, cover all UI states including accessibility, and avoid implementation-detail assertions. This catches regressions before production.