React Testing Library And Jest- The Complete Guide -

expect(screen.getByText('Loading...')).toBeInTheDocument()

// Test error states render(<Component onError=mockError />) // Don't test internal state expect(component.state('isOpen')).toBe(true) // Don't use testid as default screen.getByTestId('submit-button')

export default testEnvironment: 'jsdom', setupFilesAfterEnv: ['<rootDir>/src/setupTests.js'], transform: tsx)$': 'babel-jest', ,

expect(await screen.findByText('Valid email required')).toBeInTheDocument() ) ✅ DO // Query by accessible name screen.getByRole('button', name: /submit/i ) // Use findBy for async elements expect(await screen.findByText('Loaded')).toBeInTheDocument() React Testing Library and Jest- The Complete Guide

import render, screen from '@testing-library/react' import UserProfile from './UserProfile' // Mock fetch globally global.fetch = jest.fn()

const button = screen.getByRole('button', name: /click me/i ) expect(button).toBeInTheDocument()

// Test behavior, not implementation expect(screen.getByText('Welcome John')).toBeInTheDocument() expect(screen

render(<UserProfile userId=1 />)

test('loads and displays user', async () => const mockUser = name: 'John Doe' fetch.mockResolvedValueOnce( json: async () => mockUser, )

// Use userEvent instead of fireEvent await user.click(button) Component onError=mockError /&gt

test('should increment counter', () => const result = renderHook(() => useCounter(0))

// Test const customRender = (ui, providerProps, ...renderOptions ) => return render( <ThemeProvider ...providerProps>ui</ThemeProvider>, renderOptions )

// Wait for the user name to appear expect(await screen.findByText('John Doe')).toBeInTheDocument()

// Don't test props passed to children expect(ChildComponent).toHaveBeenCalledWith( prop: 'value' )