Write comprehensive unit tests with high coverage using testing frameworks like Jest, pytest, JUnit, or RSpec. Use when writing tests for functions, classes, components, or establishing testing standards.

Unit Testing Framework Table of Contents [Overview]( overview) [When to Use]( when to use) [Quick Start]( quick start) [Reference Guides]( reference guides) [Best Practices]( best practices) Overview Write effective unit tests that are fast, isolated, readable, and maintainable following industry best practices and AAA (Arrange Act Assert) pattern. When to Use Writing tests for new code Improving test coverage Establishing testing standards Refactoring with test safety Implementing TDD (Test Driven Development) Creating test utilities and mocks Quick Start Minimal working example: Reference Guides Detailed implementations in the references/ directory: Guide Contents [Test Structure (AAA Pattern)](references/test structure aaa pattern.md) Test Structure (AAA Pattern) [Test Cases by Language](references/test cases by language.md) Test Cases by Language [Mocking & Test Doubles](references/mocking test doubles.md) Mocking & Test Doubles [Testing Async Code](references/testing async code.md) Testing Async Code, Test Coverage [Testing Edge Cases](references/testing edge cases.md) Testing Edge Cases [Example: Complete Test Suite](references/example complete test suite.md) import { UserService } from "./user service"; Best Practices ✅ DO Write tests before or alongside code (TDD) Test one thing per test Use descriptive test names Follow AAA pattern Test edge cases and error conditions Keep tests isolated and independent Use setup/teardown appropriately Mock external dependencies Aim for high coverage on critical paths Make tests fast (< 10ms each) Use parameterized tests for similar cases Test public interfaces, not implementation ❌ DON'T Test implementation details Write tests that depend on each other Ignore failing tests Test third party library code Use real databases/APIs in unit tests Make tests too complex Skip edge cases Forget to clean up resources Test everything (focus on business logic) Write flaky tests

unit-testing-framework