Javascript Typescript Jest

The javascript-typescript-jest skill provides best practices for writing unit tests in JavaScript and TypeScript projects using the Jest testing framework, covering test structure, mocking strategies, async testing, and React component testing. It's designed for developers building applications with Jest who need guidance on organizing tests, isolating dependencies through mocking, and using appropriate matchers and testing patterns. This skill solves the problem of writing ineffective or poorly organized tests by establishing conventions for test naming, file placement, mock management, and testing different code types.

skills.sh installs: 14.5K
GitHub stars: 41K
last updated: Aug 21, 2026

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Install

$ npx -y skills add github/awesome-copilot --skill javascript-typescript-jest --agent claude-code

Installs into .claude/skills of the current project.

Files

Test Structure

Name test files with .test.ts or .test.js suffix
Place test files next to the code they test or in a dedicated __tests__ directory
Use descriptive test names that explain the expected behavior
Use nested describe blocks to organize related tests
Follow the pattern: describe('Component/Function/Class', () => { it('should do something', () => {}) })

Effective Mocking

Mock external dependencies (APIs, databases, etc.) to isolate your tests
Use jest.mock() for module-level mocks
Use jest.spyOn() for specific function mocks
Use mockImplementation() or mockReturnValue() to define mock behavior
Reset mocks between tests with jest.resetAllMocks() in afterEach

Testing Async Code

Always return promises or use async/await syntax in tests
Use resolves/rejects matchers for promises
Set appropriate timeouts for slow tests with jest.setTimeout()

Snapshot Testing

Use snapshot tests for UI components or complex objects that change infrequently
Keep snapshots small and focused
Review snapshot changes carefully before committing

SKILL.md on GitHub