if (!user) return <div>Loading...</div> return <div>user.name</div>

await user.click(button) expect(handleClick).toHaveBeenCalledTimes(1) ) Priority Order (get by accessibility first) | Query | Returns | When to use | |-------|---------|--------------| | getByRole | Element | Most preferred - accessible to screen readers | | getByLabelText | Input/textarea | Form fields with labels | | getByPlaceholderText | Input | Fallback when no label | | getByText | Element | Buttons, paragraphs, headings | | getByDisplayValue | Input | Current value of form field | | getByAltText | Image | Images with alt text | | getByTitle | Element | Title attribute | | getByTestId | Element | Last resort - avoid when possible | Query Variants // Single element (throws error if not found) screen.getByRole('button') // Multiple elements screen.getAllByRole('listitem')

const button = screen.getByRole('button') expect(button).toHaveTextContent('OFF')

export default testEnvironment: 'jsdom', setupFilesAfterEnv: ['<rootDir>/src/setupTests.js'], transform: jsx,

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

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

render(<UserProfile userId=1 />)

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