shallowWrapper是空的，正在测试快照Jest/Ezyme

Question

我不知道为什么在运行快照测试时会得到空的shallowWrapper对象，我使用的是Jest和Enzyme：

我在App.test.js.snap文件中得到的东西：

// Jest Snapshot v1, "goo.gl/fbAQLP"
exports[`renders App component 1`] = `ShallowWrapper {}`;

mypackage.json文件：

{
"name": "test",
"version": "0.1.0",
"private": true,
"dependencies": {
"@fortawesome/fontawesome-svg-core": "^1.2.30",
"@fortawesome/free-solid-svg-icons": "^5.14.0",
"@fortawesome/react-fontawesome": "^0.1.11",
"@testing-library/jest-dom": "^4.2.4",
"@testing-library/react": "^9.3.2",
"@testing-library/user-event": "^7.1.2",
"bootstrap": "^4.5.2",
"install": "^0.13.0",
"npm": "^6.14.8",
"react": "^16.13.1",
"react-bootstrap": "^1.3.0",
"react-dom": "^16.13.1",
"react-router-dom": "^5.2.0",
"react-scripts": "^4.0.0-next.98"
},
"scripts": {
"start": "react-scripts start",
"build": "react-scripts build",
"test": "react-scripts test --env=jsdom",
"eject": "react-scripts eject"
},
"eslintConfig": {
"extends": "react-app"
},
"browserslist": {
"production": [
">0.2%",
"not dead",
"not op_mini all"
],
"development": [
"last 1 chrome version",
"last 1 firefox version",
"last 1 safari version"
]
},
"devDependencies": {
"enzyme": "^3.11.0",
"enzyme-adapter-react-16": "^1.15.4",
"jest": "^26.4.2"
}
}

App.test.js文件

import { shallow } from 'enzyme';
import React from 'react';
import App from './App';

it('renders App component', () => {
expect(shallow(<App />)).toMatchSnapshot();
})

setupTests.js文件：

import { configure } from 'enzyme';
import Adapter from 'enzyme-adapter-react-16';
configure({ 
adapter: new Adapter()
});

为什么我得到了那个空的shallowWrapper对象，经过一番搜索，我怀疑是jost的版本，但即使降级也没有解决它。

Answer 1

我遇到了类似的问题，玩jest帮助我解决了这个问题。我建议你可以清除jest缓存，然后使用jest --clearCache && jest -u更新快照，然后运行测试。

同样对于您的快照，我建议您使用enzyme-to-json串行器(https://www.npmjs.com/package/enzyme-to-json)并将您的测试修改为：

import { shallow } from 'enzyme';
import React from 'react';
import App from './App';
import { shallowToJson } from 'enzyme-to-json';
it('renders App component', () => {
const app = shallow(<App />);
expect(shallowToJson(app)).toMatchSnapshot();
})

Answer 2

浅层((确实返回了输出。Shallow充当具有渲染输出的包装器实例。您可以使用带有debug((的浅层((方法来查看打印出的内容。如果您想查看渲染的输出，可以在expect((方法中使用shallow((.html((来再次测试。