react-testing-library/src/__tests__/render.js

import * as React from 'react'
import ReactDOM from 'react-dom'
import ReactDOMServer from 'react-dom/server'
import {fireEvent, render, screen, configure} from '../'

const isReact18 = React.version.startsWith('18.')
const isReact19 = React.version.startsWith('19.')

const testGateReact18 = isReact18 ? test : test.skip
const testGateReact19 = isReact19 ? test : test.skip

describe('render API', () => {
  let originalConfig
  beforeEach(() => {
    // Grab the existing configuration so we can restore
    // it at the end of the test
    configure(existingConfig => {
      originalConfig = existingConfig
      // Don't change the existing config
      return {}
    })
  })

  afterEach(() => {
    configure(originalConfig)
  })

  test('renders div into document', () => {
    const ref = React.createRef()
    const {container} = render(<div ref={ref} />)
    expect(container.firstChild).toBe(ref.current)
  })

  test('works great with react portals', () => {
    class MyPortal extends React.Component {
      constructor(...args) {
        super(...args)
        this.portalNode = document.createElement('div')
        this.portalNode.dataset.testid = 'my-portal'
      }
      componentDidMount() {
        document.body.appendChild(this.portalNode)
      }
      componentWillUnmount() {
        this.portalNode.parentNode.removeChild(this.portalNode)
      }
      render() {
        return ReactDOM.createPortal(
          <Greet greeting="Hello" subject="World" />,
          this.portalNode,
        )
      }
    }

    function Greet({greeting, subject}) {
      return (
        <div>
          <strong>
            {greeting} {subject}
          </strong>
        </div>
      )
    }

    const {unmount} = render(<MyPortal />)
    expect(screen.getByText('Hello World')).toBeInTheDocument()
    const portalNode = screen.getByTestId('my-portal')
    expect(portalNode).toBeInTheDocument()
    unmount()
    expect(portalNode).not.toBeInTheDocument()
  })

  test('returns baseElement which defaults to document.body', () => {
    const {baseElement} = render(<div />)
    expect(baseElement).toBe(document.body)
  })

  test('supports fragments', () => {
    class Test extends React.Component {
      render() {
        return (
          <div>
            <code>DocumentFragment</code> is pretty cool!
          </div>
        )
      }
    }

    const {asFragment} = render(<Test />)
    expect(asFragment()).toMatchSnapshot()
  })

  test('renders options.wrapper around node', () => {
    const WrapperComponent = ({children}) => (
      <div data-testid="wrapper">{children}</div>
    )

    const {container} = render(<div data-testid="inner" />, {
      wrapper: WrapperComponent,
    })

    expect(screen.getByTestId('wrapper')).toBeInTheDocument()
    expect(container.firstChild).toMatchInlineSnapshot(`
    <div
      data-testid=wrapper
    >
      <div
        data-testid=inner
      />
    </div>
  `)
  })

  test('renders options.wrapper around node when reactStrictMode is true', () => {
    configure({reactStrictMode: true})

    const WrapperComponent = ({children}) => (
      <div data-testid="wrapper">{children}</div>
    )
    const {container} = render(<div data-testid="inner" />, {
      wrapper: WrapperComponent,
    })

    expect(screen.getByTestId('wrapper')).toBeInTheDocument()
    expect(container.firstChild).toMatchInlineSnapshot(`
    <div
      data-testid=wrapper
    >
      <div
        data-testid=inner
      />
    </div>
  `)
  })

  test('renders twice when reactStrictMode is true', () => {
    configure({reactStrictMode: true})

    const spy = jest.fn()
    function Component() {
      spy()
      return null
    }

    render(<Component />)
    expect(spy).toHaveBeenCalledTimes(2)
  })

  test('flushes useEffect cleanup functions sync on unmount()', () => {
    const spy = jest.fn()
    function Component() {
      React.useEffect(() => spy, [])
      return null
    }
    const {unmount} = render(<Component />)
    expect(spy).toHaveBeenCalledTimes(0)

    unmount()

    expect(spy).toHaveBeenCalledTimes(1)
  })

  test('can be called multiple times on the same container', () => {
    const container = document.createElement('div')

    const {unmount} = render(<strong />, {container})

    expect(container).toContainHTML('<strong></strong>')

    render(<em />, {container})

    expect(container).toContainHTML('<em></em>')

    unmount()

    expect(container).toBeEmptyDOMElement()
  })

  test('hydrate will make the UI interactive', () => {
    function App() {
      const [clicked, handleClick] = React.useReducer(n => n + 1, 0)

      return (
        <button type="button" onClick={handleClick}>
          clicked:{clicked}
        </button>
      )
    }
    const ui = <App />
    const container = document.createElement('div')
    document.body.appendChild(container)
    container.innerHTML = ReactDOMServer.renderToString(ui)

    expect(container).toHaveTextContent('clicked:0')

    render(ui, {container, hydrate: true})

    fireEvent.click(container.querySelector('button'))

    expect(container).toHaveTextContent('clicked:1')
  })

  test('hydrate can have a wrapper', () => {
    const wrapperComponentMountEffect = jest.fn()
    function WrapperComponent({children}) {
      React.useEffect(() => {
        wrapperComponentMountEffect()
      })

      return children
    }
    const ui = <div />
    const container = document.createElement('div')
    document.body.appendChild(container)
    container.innerHTML = ReactDOMServer.renderToString(ui)

    render(ui, {container, hydrate: true, wrapper: WrapperComponent})

    expect(wrapperComponentMountEffect).toHaveBeenCalledTimes(1)
  })

  testGateReact18('legacyRoot uses legacy ReactDOM.render', () => {
    expect(() => {
      render(<div />, {legacyRoot: true})
    }).toErrorDev(
      [
        "Warning: ReactDOM.render is no longer supported in React 18. Use createRoot instead. Until you switch to the new API, your app will behave as if it's running React 17. Learn more: https://reactjs.org/link/switch-to-createroot",
      ],
      {withoutStack: true},
    )
  })

  testGateReact19('legacyRoot throws', () => {
    expect(() => {
      render(<div />, {legacyRoot: true})
    }).toThrowErrorMatchingInlineSnapshot(
      `\`legacyRoot: true\` is not supported in this version of React. If your app runs React 19 or later, you should remove this flag. If your app runs React 18 or earlier, visit https://react.dev/blog/2022/03/08/react-18-upgrade-guide for upgrade instructions.`,
    )
  })

  testGateReact18('legacyRoot uses legacy ReactDOM.hydrate', () => {
    const ui = <div />
    const container = document.createElement('div')
    container.innerHTML = ReactDOMServer.renderToString(ui)
    expect(() => {
      render(ui, {container, hydrate: true, legacyRoot: true})
    }).toErrorDev(
      [
        "Warning: ReactDOM.hydrate is no longer supported in React 18. Use hydrateRoot instead. Until you switch to the new API, your app will behave as if it's running React 17. Learn more: https://reactjs.org/link/switch-to-createroot",
      ],
      {withoutStack: true},
    )
  })

  testGateReact19('legacyRoot throws even with hydrate', () => {
    const ui = <div />
    const container = document.createElement('div')
    container.innerHTML = ReactDOMServer.renderToString(ui)
    expect(() => {
      render(ui, {container, hydrate: true, legacyRoot: true})
    }).toThrowErrorMatchingInlineSnapshot(
      `\`legacyRoot: true\` is not supported in this version of React. If your app runs React 19 or later, you should remove this flag. If your app runs React 18 or earlier, visit https://react.dev/blog/2022/03/08/react-18-upgrade-guide for upgrade instructions.`,
    )
  })

  test('reactStrictMode in renderOptions has precedence over config when rendering', () => {
    const wrapperComponentMountEffect = jest.fn()
    function WrapperComponent({children}) {
      React.useEffect(() => {
        wrapperComponentMountEffect()
      })

      return children
    }
    const ui = <div />
    configure({reactStrictMode: false})

    render(ui, {wrapper: WrapperComponent, reactStrictMode: true})

    expect(wrapperComponentMountEffect).toHaveBeenCalledTimes(2)
  })

  test('reactStrictMode in config is used when renderOptions does not specify reactStrictMode', () => {
    const wrapperComponentMountEffect = jest.fn()
    function WrapperComponent({children}) {
      React.useEffect(() => {
        wrapperComponentMountEffect()
      })

      return children
    }
    const ui = <div />
    configure({reactStrictMode: true})

    render(ui, {wrapper: WrapperComponent})

    expect(wrapperComponentMountEffect).toHaveBeenCalledTimes(2)
  })
})