feat(unmount): add unmount to render object

README.md

@@ -127,6 +127,21 @@ The containing DOM node of your rendered React Element (rendered using
 
 > Tip: To get the root element of your rendered element, use `container.firstChild`.
 
+#### `unmount`
+
+This will cause the rendered component to be unmounted. This is useful for
+testing what happens when your component is removed from the page (like testing
+that you don't leave event handlers hanging around causing memory leaks).
+
+> This method is a pretty small abstraction over
+> `ReactDOM.unmountComponentAtNode`
+
+```javascript
+const {container, unmount} = render(<Login />)
+unmount()
+// your component has been unmounted and now: container.innerHTML === ''
+```
+
 #### `queryByTestId`
 
 A shortcut to `` container.querySelector(`[data-testid="${yourId}"]`) ``. Read
@@ -270,7 +285,9 @@ Or you could include the index or an ID in your attribute:
 And then you could use the `queryByTestId`:
 
 ```javascript
-const items = [/* your items */]
+const items = [
+  /* your items */
+]
 const {queryByTestId} = render(/* your component with the items */)
 const thirdItem = queryByTestId(`item-${items[2].id}`)
 ```

src/__tests__/stopwatch.js

@@ -0,0 +1,59 @@
+import React from 'react'
+import {render, Simulate} from '../'
+
+class StopWatch extends React.Component {
+  state = {lapse: 0, running: false}
+  handleRunClick = () => {
+    this.setState(state => {
+      if (state.running) {
+        clearInterval(this.timer)
+      } else {
+        const startTime = Date.now() - this.state.lapse
+        this.timer = setInterval(() => {
+          this.setState({lapse: Date.now() - startTime})
+        })
+      }
+      return {running: !state.running}
+    })
+  }
+  handleClearClick = () => {
+    clearInterval(this.timer)
+    this.setState({lapse: 0, running: false})
+  }
+  componentWillUnmount() {
+    clearInterval(this.timer)
+  }
+  render() {
+    const {lapse, running} = this.state
+    return (
+      <div>
+        <span>{lapse}ms</span>
+        <button onClick={this.handleRunClick} data-testid="start-stop-button">
+          {running ? 'Stop' : 'Start'}
+        </button>
+        <button onClick={this.handleClearClick} data-testid="clear-button">
+          Clear
+        </button>
+      </div>
+    )
+  }
+}
+
+const wait = time => new Promise(resolve => setTimeout(resolve, time))
+
+test('unmounts a component', async () => {
+  jest.spyOn(console, 'error').mockImplementation(() => {})
+  const {unmount, queryByTestId, container} = render(<StopWatch />)
+  Simulate.click(queryByTestId('start-stop-button'))
+  unmount()
+  // hey there reader! You don't need to have an assertion like this one
+  // this is just me making sure that the unmount function works.
+  // You don't need to do this in your apps. Just rely on the fact that this works.
+  expect(container.innerHTML).toBe('')
+  // just wait to see if the interval is cleared or not
+  // if it's not, then we'll call setState on an unmounted component
+  // and get an error.
+  await wait()
+  // eslint-disable-next-line no-console
+  expect(console.error).not.toHaveBeenCalled()
+})

src/index.js

@@ -15,6 +15,7 @@ function render(ui, {container = document.createElement('div')} = {}) {
   ReactDOM.render(ui, container)
   return {
     container,
+    unmount: () => ReactDOM.unmountComponentAtNode(container),
     queryByTestId: queryDivByTestId.bind(null, container),
   }
 }