0137-javascript-testing-patterns

What problem does it solve?

It reduces flaky, incomplete, and poorly structured test suites by showing how to set up modern JavaScript testing with clear patterns for unit, integration, and end-to-end coverage.

Core Features & Use Cases

• Testing framework setup (Jest/Vitest): Configure TypeScript-friendly test runners and consistent coverage thresholds.
• Deterministic unit testing: Apply Arrange-Act-Assert with pure function, class, and async testing patterns.
• Realistic integration coverage: Use supertest-style API testing and database integration approaches with truncation/teardown hygiene.
• Mocking strategies: Mock modules and dependencies, and use spies to validate observable behavior.
• Frontend testing with Testing Library: Query by role/placeholder/test id sparingly and test hooks with renderHook + act.
• Test data quality: Use faker-based fixtures/factories for repeatable, realistic inputs.

Quick Start

Generate a Jest or Vitest test suite for your existing JavaScript/TypeScript codebase using the provided patterns for unit tests, async behavior, mocking, and (when applicable) integration/API tests.