testing-strategy

The test pyramid distributes testing effort as 70% unit tests, 20% integration tests, and 10% end-to-end tests. This structure balances speed, coverage, and confidence by testing business logic in isolation first, then interactions between components, then complete user workflows—reducing feedback time while catching real-world failures.

Red-Green-Refactor is the core TDD workflow: write a failing test (red), write minimal code to pass it (green), then clean up the implementation (refactor). This cycle ensures tests drive design, maintains high coverage, and prevents over-engineering by committing only to code that satisfies a concrete requirement.

Mock external services, databases, and third-party APIs to isolate units and speed tests; test real interactions at the integration layer where components actually collaborate. Mocking prevents flaky tests and uncontrolled side effects, while integration tests catch issues that isolation hides—apply each strategically by layer.

Coverage tools report what code paths your tests exercise, but high percentages don't guarantee quality. Set goals aligned to your test pyramid—aim for high coverage on business logic and critical paths, lower on infrastructure. Pair metrics with code review and failure analysis to ensure tests catch real bugs.

Yes, testing strategies are language-agnostic and work directly with TypeScript and JavaScript. The test pyramid, TDD cycles, AAA pattern, and mocking practices apply across Node.js backends, React frontends, and full-stack applications with standard test runners like Jest, Mocha, or Vitest.

Run your test suite automatically on every commit: unit tests first for fast feedback, then integration and end-to-end tests in parallel. Fail the build on test failures, coverage drops, or flaky results. This gates code quality and prevents regressions from reaching production.