---
id: ssh-javascript-typescript-jest
name: "javascript-typescript-jest"
url: https://skills.yangsir.net/skill/ssh-javascript-typescript-jest
author: github
domain: testing
tags: ["javascript", "typescript", "jest", "unit-testing", "nodejs"]
install_count: 10600
rating: 4.50 (317 reviews)
github: https://github.com/github/awesome-copilot
---

# javascript-typescript-jest

> 提供使用Jest编写JavaScript/TypeScript测试的最佳实践，包括模拟策略、测试结构和常见模式。

**Stats**: 10,600 installs · 4.5/5 (317 reviews)

## Before / After 对比

### Jest测试JavaScript/TypeScript最佳实践

## Readme

### 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

### Testing React Components
- Use React Testing Library over Enzyme for testing components
- Test user behavior and component accessibility
- Query elements by accessibility roles, labels, or text content
- Use `userEvent` over `fireEvent` for more realistic user interactions

## Common Jest Matchers
- Basic: `expect(value).toBe(expected)`, `expect(value).toEqual(expected)`
- Truthiness: `expect(value).toBeTruthy()`, `expect(value).toBeFalsy()`
- Numbers: `expect(value).toBeGreaterThan(3)`, `expect(value).toBeLessThanOrEqual(3)`
- Strings: `expect(value).toMatch(/pattern/)`, `expect(value).toContain('substring')`
- Arrays: `expect(array).toContain(item)`, `expect(array).toHaveLength(3)`
- Objects: `expect(object).toHaveProperty('key', value)`
- Exceptions: `expect(fn).toThrow()`, `expect(fn).toThrow(Error)`
- Mock functions: `expect(mockFn).toHaveBeenCalled()`, `expect(mockFn).toHaveBeenCalledWith(arg1, arg2)`


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*Source: https://skills.yangsir.net/skill/ssh-javascript-typescript-jest*
*Markdown mirror: https://skills.yangsir.net/api/skill/ssh-javascript-typescript-jest/markdown*