我有一个使用 React 作为视图层的项目。为了测试它,我使用了 mocha、karma、karma-webpack 等。出于某种原因,在 React 16+ 中,karma 报告afterEach
说 已经为两个规范运行了 3 次。这仅在 React 16+ 中发生,并且仅在process.env.NODE_ENV
isdevelopment
和not production
时发生。
在之前对该问题的探索中,规范失败的原因可能会级联并污染后续规范。为了帮助确定根本原因,这是我能找到的最简单的例子。
我试图追踪这种行为,但被业力和套接字内部和周围的复杂性所困扰。考虑下面的示例,目前可在https://github.com/jneander/react-mocha获得。
Example.js
import React, {Component} from 'react'
export default class Example extends Component {
render() {
try {
return (
<div>{this.props.foo.bar}</div>
)
} catch(e) {
console.log(e) // for logging purposes
throw e
}
}
}
Example.spec.js
import {expect} from 'chai'
import React from 'react'
import ReactDOM from 'react-dom'
class ExampleWrapper extends React.Component {
constructor(props) {
super(props)
this.state = {
error: false
}
}
componentDidCatch(error) {
console.log('there was a problem')
this.setState({
error: true
})
}
render() {
console.log('rendering!')
if (this.state.error) {
console.log('- rendering the error version')
return <div>An error occurred during render</div>
}
console.log('- rendering the real version')
return (
<Example {...this.props} />
)
}
}
import Example from './Example'
describe('Example', () => {
let $container
beforeEach(() => {
console.log('beforeEach')
$container = document.createElement('div')
document.body.appendChild($container)
})
afterEach(() => {
console.log('afterEach')
ReactDOM.unmountComponentAtNode($container)
$container.remove()
})
async function mount(props) {
return new Promise((resolve, reject) => {
const done = () => {
console.log('done rendering')
resolve()
}
ReactDOM.render(<ExampleWrapper {...props} />, $container, done)
})
}
it('fails this spec', async () => {
console.log('start test 1')
await mount({})
expect(true).to.be.true
})
it('also fails, but because of the first spec', async () => {
console.log('start test 2')
await mount({foo: {}})
expect(true).to.be.true
})
})
规格输出如下:
LOG LOG: 'beforeEach'
LOG LOG: 'start test 1'
LOG LOG: 'rendering!'
LOG LOG: '- rendering the real version'
Example
✗ fails this spec
Error: Uncaught TypeError: Cannot read property 'bar' of undefined (src/Example.spec.js:35380)
at Object.invokeGuardedCallbackDev (src/Example.spec.js:16547:16)
at invokeGuardedCallback (src/Example.spec.js:16600:31)
at replayUnitOfWork (src/Example.spec.js:31930:5)
at renderRoot (src/Example.spec.js:32733:11)
at performWorkOnRoot (src/Example.spec.js:33572:7)
at performWork (src/Example.spec.js:33480:7)
at performSyncWork (src/Example.spec.js:33452:3)
at requestWork (src/Example.spec.js:33340:5)
at scheduleWork (src/Example.spec.js:33134:5)
ERROR LOG: 'The above error occurred in the <Example> component:
in Example (created by ExampleWrapper)
in ExampleWrapper
React will try to recreate this component tree from scratch using the error boundary you provided, ExampleWrapper.'
LOG LOG: 'there was a problem'
LOG LOG: 'done rendering'
LOG LOG: 'rendering!'
LOG LOG: '- rendering the error version'
LOG LOG: 'afterEach'
LOG LOG: 'beforeEach'
LOG LOG: 'start test 2'
LOG LOG: 'rendering!'
LOG LOG: '- rendering the real version'
LOG LOG: 'done rendering'
✓ also fails, but because of the first spec
✓ also fails, but because of the first spec
LOG LOG: 'afterEach'
LOG LOG: 'afterEach'
Chrome 69.0.3497 (Mac OS X 10.13.6): Executed 3 of 2 (1 FAILED) (0.014 secs / NaN secs)
TOTAL: 1 FAILED, 2 SUCCESS
1) fails this spec
Example
Error: Uncaught TypeError: Cannot read property 'bar' of undefined (src/Example.spec.js:35380)
at Object.invokeGuardedCallbackDev (src/Example.spec.js:16547:16)
at invokeGuardedCallback (src/Example.spec.js:16600:31)
at replayUnitOfWork (src/Example.spec.js:31930:5)
at renderRoot (src/Example.spec.js:32733:11)
at performWorkOnRoot (src/Example.spec.js:33572:7)
at performWork (src/Example.spec.js:33480:7)
at performSyncWork (src/Example.spec.js:33452:3)
at requestWork (src/Example.spec.js:33340:5)
at scheduleWork (src/Example.spec.js:33134:5)
是什么导致重复报告?
为什么这发生在 React 16+ 而不是 React 15?
我该如何解决这个问题?