React Testing Library And Jest- The Complete Guide Apr 2026

await user.type(screen.getByLabelText(/email/i), 'user@example.com') await user.type(screen.getByLabelText(/password/i), 'secret123') await user.click(screen.getByRole('button', name: /submit/i ))

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

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

const button = screen.getByRole('button', name: /click me/i ) expect(button).toBeInTheDocument() React Testing Library and Jest- The Complete Guide

// Don't use act directly (userEvent handles it) act(() => render(<Component />) )

act(() => result.current.increment() )

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

render(<Button onClick=handleClick>Click Me</Button>)

act(() => jest.advanceTimersByTime(1000) )

test('loads and displays user', async () => const mockUser = name: 'John Doe' fetch.mockResolvedValueOnce( json: async () => mockUser, ) 'secret123') await user.click(screen.getByRole('button'

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

import userEvent from '@testing-library/user-event' test('form submission', async () => const user = userEvent.setup() render(<LoginForm />)

expect(result.current.count).toBe(1) ) Mock functions with Jest const mockFn = jest.fn() mockFn('hello') expect(mockFn).toHaveBeenCalledWith('hello') expect(mockFn).toHaveBeenCalledTimes(1) // Mock return value jest.fn().mockReturnValue('fixed value') jest.fn().mockResolvedValue('async value') jest.fn().mockImplementation(arg => arg * 2) Mock modules // Mock entire module jest.mock('../api', () => ( fetchUser: jest.fn(), )) // Mock with dynamic implementation jest.mock('axios', () => ( get: jest.fn(() => Promise.resolve( data: id: 1 )), )) Mock timers jest.useFakeTimers() test('delayed action', () => render(<DelayedComponent />)

test('toggles state on click', async () => const user = userEvent.setup() render(<Toggle />)

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