File size: 1,637 Bytes
1e92f2d |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 |
import * as React from 'react'
import {render, fireEvent, screen} 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}>
{running ? 'Stop' : 'Start'}
</button>
<button onClick={this.handleClearClick}>Clear</button>
</div>
)
}
}
const sleep = t => new Promise(resolve => setTimeout(resolve, t))
test('unmounts a component', async () => {
const {unmount, container} = render(<StopWatch />)
fireEvent.click(screen.getByText('Start'))
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).toBeEmptyDOMElement()
// 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 sleep(5)
})
|