Test Patterns

Unit, integration, and E2E testing patterns with framework-specific guidance. Use when asked to "write tests", "add test coverage", "testing strategy", "test this function", "create test suite", "fix flaky tests", or "improve test quality".

Write, run, and manage unit, integration, and E2E tests across TypeScript, Python, and Swift using recommended frameworks.

Jest best practices, patterns, and API guidance for JavaScript/TypeScript testing. Covers mock design, async testing, matchers, timer mocks, snapshots, modul...

Write clean, maintainable pytest tests using Fake-based testing, contract testing, and dependency injection patterns. Use when setting up test suites for Pyt...

WHAT: Production-ready Node.js backend patterns - Express/Fastify setup, layered architecture, middleware, error handling, validation, database integration, authentication, and caching. WHEN: User is building REST APIs, setting up Node.js servers, implementing authentication, integrating databases, adding validation/caching, or structuring backend applications. KEYWORDS: nodejs, node, express, fastify, typescript, api, rest, middleware, authentication, jwt, validation, zod, postgres, mongod

Testing patterns for Zod schemas using Jest and Vitest. Covers schema correctness testing, mock data generation, error assertion patterns, integration testin...