React Testing Library And Jest- The Complete Guide -

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

// 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') React Testing Library and Jest- The Complete Guide

// Test behavior, not implementation expect(screen.getByText('Welcome John')).toBeInTheDocument() test('loads and displays user', async () =&gt; const

// Test const customRender = (ui, providerProps, ...renderOptions ) => return render( <ThemeProvider ...providerProps>ui</ThemeProvider>, renderOptions ) test('loads and displays user'

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

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

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