test: Backport tests using the full timer matrix (#962)

Author: eps1lon

src/__tests__/end-to-end.js

@@ -1,5 +1,5 @@
 import * as React from 'react'
-import {render, waitForElementToBeRemoved, screen} from '../'
+import {render, waitForElementToBeRemoved, screen, waitFor} from '../'
 
 const fetchAMessage = () =>
   new Promise(resolve => {
@@ -11,27 +11,63 @@ const fetchAMessage = () =>
     }, randomTimeout)
   })
 
-class ComponentWithLoader extends React.Component {
-  state = {loading: true}
-  async componentDidMount() {
-    const data = await fetchAMessage()
-    this.setState({data, loading: false}) // eslint-disable-line
-  }
-  render() {
-    if (this.state.loading) {
-      return <div>Loading...</div>
+function ComponentWithLoader() {
+  const [state, setState] = React.useState({data: undefined, loading: true})
+  React.useEffect(() => {
+    let cancelled = false
+    fetchAMessage().then(data => {
+      if (!cancelled) {
+        setState({data, loading: false})
+      }
+    })
+
+    return () => {
+      cancelled = true
     }
-    return (
-      <div data-testid="message">
-        Loaded this message: {this.state.data.returnedMessage}!
-      </div>
-    )
+  }, [])
+
+  if (state.loading) {
+    return <div>Loading...</div>
   }
+
+  return (
+    <div data-testid="message">
+      Loaded this message: {state.data.returnedMessage}!
+    </div>
+  )
 }
 
-test('it waits for the data to be loaded', async () => {
-  render(<ComponentWithLoader />)
-  const loading = () => screen.getByText('Loading...')
-  await waitForElementToBeRemoved(loading)
-  expect(screen.getByTestId('message')).toHaveTextContent(/Hello World/)
+describe.each([
+  ['real timers', () => jest.useRealTimers()],
+  ['fake legacy timers', () => jest.useFakeTimers('legacy')],
+  ['fake modern timers', () => jest.useFakeTimers('modern')],
+])('it waits for the data to be loaded using %s', (label, useTimers) => {
+  beforeEach(() => {
+    useTimers()
+  })
+
+  afterEach(() => {
+    jest.useRealTimers()
+  })
+
+  test('waitForElementToBeRemoved', async () => {
+    render(<ComponentWithLoader />)
+    const loading = () => screen.getByText('Loading...')
+    await waitForElementToBeRemoved(loading)
+    expect(screen.getByTestId('message')).toHaveTextContent(/Hello World/)
+  })
+
+  test('waitFor', async () => {
+    render(<ComponentWithLoader />)
+    const message = () => screen.getByText(/Loaded this message:/)
+    await waitFor(message)
+    expect(screen.getByTestId('message')).toHaveTextContent(/Hello World/)
+  })
+
+  test('findBy', async () => {
+    render(<ComponentWithLoader />)
+    await expect(screen.findByTestId('message')).resolves.toHaveTextContent(
+      /Hello World/,
+    )
+  })
 })