我有一个简单的测试我试图通过Enzyme / mocha / chai。这是错误:
1) <PostList /> should have a container for holding posts:
TypeError: Cannot read property 'length' of undefined
at PostList.render (D:/mydocs/webdev/gitprojs/ReactBlogFinal/views/PostList/PostList.jsx:13:9)
at node_modules\react-test-renderer\lib\shallow\ReactCompositeComponent.js:795:21
at measureLifeCyclePerf (node_modules\react-test-renderer\lib\shallow\ReactCompositeComponent.js:75:12)
at ShallowComponentWrapper._renderValidatedComponentWithoutOwnerOrContext (node_modules\react-test-renderer\lib\shallow\ReactCompositeComponent.js:794:25)
at ShallowComponentWrapper.performInitialMount (node_modules\react-test-renderer\lib\shallow\ReactCompositeComponent.js:361:30)
at ShallowComponentWrapper.mountComponent (node_modules\react-test-renderer\lib\shallow\ReactCompositeComponent.js:257:21)
at Object.mountComponent (node_modules\react-test-renderer\lib\shallow\ReactReconciler.js:45:35)
at ReactShallowRenderer._render (node_modules\react-test-renderer\lib\shallow\ReactShallowRenderer.js:138:23)
at _batchedRender (node_modules\react-test-renderer\lib\shallow\ReactShallowRenderer.js:85:12)
at Object.batchedUpdates (node_modules\react-test-renderer\lib\shallow\ReactDefaultBatchingStrategy.js:60:14)
at Object.batchedUpdates (node_modules\react-test-renderer\lib\shallow\ReactUpdates.js:97:27)
at ReactShallowRenderer.render (node_modules\react-test-renderer\lib\shallow\ReactShallowRenderer.js:112:18)
at ReactShallowRenderer.render (node_modules\enzyme\build\react-compat.js:171:37)
at node_modules\enzyme\build\ShallowWrapper.js:128:26
at ReactDefaultBatchingStrategyTransaction.perform (node_modules\react-test-renderer\lib\shallow\Transaction.js:143:20)
at Object.batchedUpdates (node_modules\react-test-renderer\lib\shallow\ReactDefaultBatchingStrategy.js:62:26)
at Object.batchedUpdates (node_modules\react-test-renderer\lib\shallow\ReactUpdates.js:97:27)
at ReactShallowRenderer.unstable_batchedUpdates (node_modules\react-test-renderer\lib\shallow\ReactShallowRenderer.js:130
这是测试。我只是测试检查是否存在div:
import React from 'react';
import { mount, shallow, render } from 'enzyme';
import { expect } from 'chai';
import PostList from './PostList';
describe('<PostList />', () => {
it('should have a container for holding posts', () => {
const wrapper = shallow(<PostList />);
expect(wrapper.find('div')).to.have.length(1);
});
});
这是组件。这个组件将是博客帖子的容器,if语句测试posts对象的长度,如果它通过,我的post divs将开始生成。所以我知道这些帖子一开始就没有定义。 React中的错误做法是在渲染方法中使用逻辑吗?或者这是酶方面的问题?:
import React from 'react';
export default class PostList extends React.Component {
render() {
const posts = this.props.posts;
let postDivs;
if (posts.length !== 0) {
postDivs = posts.map(post => (
<div className="post-item" key={post._id}>
<h2 className="post-title">{post.title}</h2>
<h3 className="post-date">{post.date}</h3>
<h3 className="author">{post.author}</h3>
<p className="body">{post.body}</p>
</div>
));
console.log(postDivs);
}
return (
<div className="post-container">
{postDivs}
</div>
);
}
}
答案 0 :(得分:3)
您正在渲染PostList而不定义帖子(在道具上)。
const wrapper = shallow(<PostList />)
所以,this.props.posts是未定义的,你试图从未定义的变量中读取属性(长度)
1) <PostList /> should have a container for holding posts:
TypeError: Cannot read property 'length' of undefined
这导致异常并且您的测试失败
答案 1 :(得分:1)
undefined
是undefined
。 PostList.defaultProps = { posts: [] }
没有长度 - 只有字符串和数组(或带有自定义getter的一些对象)
您需要propTypes
或者您需要<PostList posts={[]} />
或者将游览测试写为if (posts !== undefined && posts.length !== 0) {
或将渲染语句设为const { posts = [] } = this.props
或Calendar time = Calendar.getInstance();
time.setTimeInMillis(System.currentTimeMillis());
time.add(Calendar.SECOND, 30);
and then using time.getTimeInMillis()
- 挑