javascript-typescript-jest

- 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', () => {}) }) - 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 - 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() - Use snapshot tests for UI components or complex objects that change infrequently - Keep snapshots small and focused - Review snapshot changes carefully before committing - 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 - Basic: expect(value).toBe(expected) , expect(value).toEqual(expected) - Truthiness: expect(value).toBeTruthy() , expect(value).toBeFalsy() -...