【问题标题】：Can't get Jest to work with Styled Components which contain theming无法让 Jest 使用包含主题的样式化组件
【发布时间】：2018-07-08 06:04:57
【问题描述】：

问题

我一直在使用 Jest 和 Enzyme 为我使用很棒的 Styled Components 库构建的 React 组件编写测试。

但是，由于我已经实现了主题化，所以我的所有测试都失败了。让我举一个例子。

这是我的 LooksBrowser 组件的代码（我已经删除了所有的导入和 prop-types 以使其更具可读性）：

const LooksBrowserWrapper = styled.div`
  position: relative;
  padding: 0 0 56.25%;
`;

const CurrentSlideWrapper = styled.div`
  position: absolute;
  top: 0;
  left: 0;
  z-index: 2;
`;

const NextSlideWrapper = CurrentSlideWrapper.extend`
  z-index: 1;
`;

const SlideImage = styled.img`
  display: block;
  width: 100%;
`;

const SlideText = styled.div`
  display: flex;
  position: absolute;
  top: 25%;
  left: ${PXToVW(72)};
  height: 25%;
  flex-direction: column;
  justify-content: center;
`;

const SlideTitle = styled.p`
  flex: 0 0 auto;
  text-transform: uppercase;
  line-height: 1;
  color: ${props => props.color};
  font-family: ${props => props.theme.LooksBrowser.SlideTitle.FontFamily};
  font-size: ${PXToVW(52)};
`;

const SlideSubtitle = SlideTitle.extend`
  font-family: ${props => props.theme.LooksBrowser.SlideSubtitle.FontFamily};
`;

export default class LooksBrowser extends React.Component {
  state = {
    currentSlide: {
      imageURL: this.props.currentSlide.imageURL,
      index: this.props.currentSlide.index,
      subtitle: this.props.currentSlide.subtitle,
      textColor: this.props.currentSlide.textColor,
      title: this.props.currentSlide.title
    },
    nextSlide: {
      imageURL: this.props.nextSlide.imageURL,
      index: this.props.nextSlide.index,
      subtitle: this.props.nextSlide.subtitle,
      textColor: this.props.nextSlide.textColor,
      title: this.props.nextSlide.title
    },
    nextSlideIsLoaded: false
  };

  componentDidMount() {
    this.setVariables();
  }

  componentWillReceiveProps(nextProps) {
    // Only update the state when the nextSlide data is different than the current nextSlide data
    // and when the LooksBrowser component isn't animating
    if (this.props.nextSlide.imageURL !== nextProps.nextSlide.imageURL && !this.isAnimating) {
      this.setState(prevState => update(prevState, {
        nextSlide: {
          imageURL: { $set: nextProps.nextSlide.imageURL },
          index: { $set: nextProps.nextSlide.index },
          subtitle: { $set: nextProps.nextSlide.subtitle },
          textColor: { $set: nextProps.nextSlide.textColor },
          title: { $set: nextProps.nextSlide.title }
        }
      }));
    }
  }

  componentDidUpdate() {
    if (!this.isAnimating) {
      if (this.state.nextSlide.imageURL !== '' && this.state.nextSlideIsLoaded) {
        // Only do the animation when the nextSlide is done loading and it defined inside of the state
        this.animateToNextSlide();
      } else if (this.state.currentSlide.imageURL !== this.props.nextSlide.imageURL && this.state.nextSlide.imageURL !== this.props.nextSlide.imageURL) {
        // This usecase is for when the LooksBrowser already received another look while still being in an animation
        // After the animation is done it checks if the new nextSlide data is different than the current currentSlide data
        // And also checks if the current nextSlide state data is different than the new nextSlide data
        // If so, it updates the nextSlide part of the state so that in the next render animateToNextSlide will be called
        this.setState(prevState => update(prevState, {
          nextSlide: {
            imageURL: { $set: this.props.nextSlide.imageURL },
            index: { $set: this.props.nextSlide.index },
            subtitle: { $set: this.props.nextSlide.subtitle },
            textColor: { $set: this.props.nextSlide.textColor },
            title: { $set: this.props.nextSlide.title }
          }
        }));
      } else if (!this.state.nextSlideIsLoaded) {
        // Reset currentSlide position to prevent 'flash'
        TweenMax.set(this.currentSlide, {
          x: '0%'
        });
      }
    }
  }

  setVariables() {
    this.TL = new TimelineMax();
    this.isAnimating = false;
  }

  nextSlideIsLoaded = () => {
    this.setState(prevState => update(prevState, {
      nextSlideIsLoaded: { $set: true }
    }));
  };

  animateToNextSlide() {
    const AnimateForward = this.state.currentSlide.index < this.state.nextSlide.index;
    this.isAnimating = true;

    this.TL.clear();
    this.TL
      .set(this.currentSlide, {
        x: '0%'
      })
      .set(this.nextSlide, {
        x: AnimateForward ? '100%' : '-100%'
      })
      .to(this.currentSlide, 0.7, {
        x: AnimateForward ? '-100%' : '100%',
        ease: Quad.easeInOut
      })
      .to(this.nextSlide, 0.7, {
        x: '0%',
        ease: Quad.easeInOut,
        onComplete: () => {
          this.isAnimating = false;
          this.setState(prevState => update(prevState, {
            currentSlide: {
              imageURL: { $set: prevState.nextSlide.imageURL },
              index: { $set: prevState.nextSlide.index },
              subtitle: { $set: prevState.nextSlide.subtitle },
              textColor: { $set: prevState.nextSlide.textColor },
              title: { $set: prevState.nextSlide.title }
            },
            nextSlide: {
              imageURL: { $set: '' },
              index: { $set: 0 },
              subtitle: { $set: '' },
              textColor: { $set: '' },
              title: { $set: '' }
            },
            nextSlideIsLoaded: { $set: false }
          }));
        }
      }, '-=0.7');
  }

  render() {
    return(
      <LooksBrowserWrapper>
        <CurrentSlideWrapper innerRef={div => this.currentSlide = div} >
          <SlideImage src={this.state.currentSlide.imageURL} alt={this.state.currentSlide.title} />
          <SlideText>
            <SlideTitle color={this.state.currentSlide.textColor}>{this.state.currentSlide.title}</SlideTitle>
            <SlideSubtitle color={this.state.currentSlide.textColor}>{this.state.currentSlide.subtitle}</SlideSubtitle>
          </SlideText>
        </CurrentSlideWrapper>
        {this.state.nextSlide.imageURL &&
          <NextSlideWrapper innerRef={div => this.nextSlide = div}>
            <SlideImage src={this.state.nextSlide.imageURL} alt={this.state.nextSlide.title} onLoad={this.nextSlideIsLoaded} />
            <SlideText>
              <SlideTitle color={this.state.nextSlide.textColor}>{this.state.nextSlide.title}</SlideTitle>
              <SlideSubtitle color={this.state.nextSlide.textColor}>{this.state.nextSlide.subtitle}</SlideSubtitle>
            </SlideText>
          </NextSlideWrapper>
        }
      </LooksBrowserWrapper>
    );
  }
}

现在我测试我的LooksBrowser 组件（以下是完整代码）：

import React from 'react';
import Enzyme, { mount } from 'enzyme';
import renderer from 'react-test-renderer';
import Adapter from 'enzyme-adapter-react-16';
import 'jest-styled-components';
import LooksBrowser from './../src/app/components/LooksBrowser/LooksBrowser';

Enzyme.configure({ adapter: new Adapter() });

test('Compare snapshots', () => {
  const Component = renderer.create(<LooksBrowser currentSlide={{ imageURL: 'http://localhost:3001/img/D1_VW_SPW.jpg', index: 1, subtitle: 'Where amazing happens', title: 'The United States of America', textColor: '#fff' }} nextSlide={{ imageURL: '', index: 0, subtitle: '', title: '', textColor: '' }} />);

  const Tree = Component.toJSON();
  expect(Tree).toMatchSnapshot();
});

test('Renders without crashing', () => {
  mount(<LooksBrowser currentSlide={{ imageURL: 'http://localhost:3001/img/D1_VW_SPW.jpg', index: 1, subtitle: 'Where amazing happens', title: 'The United States of America', textColor: '#fff' }} nextSlide={{ imageURL: '', index: 0, subtitle: '', title: '', textColor: '' }} />);
});

test('Check if componentDidUpdate gets called', () => {
  const spy = jest.spyOn(LooksBrowser.prototype, 'componentDidUpdate');
  const Component = mount(<LooksBrowser currentSlide={{ imageURL: 'http://localhost:3001/img/D1_VW_SPW.jpg', index: 1, subtitle: 'Where amazing happens', title: 'The United States of America', textColor: '#fff' }} nextSlide={{ imageURL: '', index: 0, subtitle: '', title: '', textColor: '' }} />);

  Component.setProps({ nextSlide: { imageURL: 'http://localhost:3001/img/D2_VW_SPW.jpg', index: 2, subtitle: 'Don\'t walk here at night', title: 'What A View', textColor: '#fff' } });
  expect(spy).toBeCalled();
});

test('Check if animateToNextSlide gets called', () => {
  const spy = jest.spyOn(LooksBrowser.prototype, 'animateToNextSlide');
  const Component = mount(<LooksBrowser currentSlide={{ imageURL: 'http://localhost:3001/img/D1_VW_SPW.jpg', index: 1, subtitle: 'Where amazing happens', title: 'The United States of America', textColor: '#fff' }} nextSlide={{ imageURL: '', index: 0, subtitle: '', title: '', textColor: '' }} />);

  Component.setProps({ nextSlide: { imageURL: 'http://localhost:3001/img/D2_VW_SPW.jpg', index: 2, subtitle: 'Don\'t walk here at night', title: 'What A View', textColor: '#fff' } });
  Component.setState({ nextSlideIsLoaded: true });
  expect(spy).toBeCalled();
});

在我实施主题之前，所有这些测试都通过了。实现主题后，每次测试都会出现以下错误：

TypeError: Cannot read property 'SlideTitle' of undefined

  44 |   line-height: 1;
  45 |   color: ${props => props.color};
> 46 |   font-family: ${props => props.theme.LooksBrowser.SlideTitle.FontFamily};
  47 |   font-size: ${PXToVW(52)};
  48 | `;
  49 |

好的，有道理。主题未定义。

解决方案一

所以经过一番谷歌搜索后，我找到了以下“解决方案”：

https://github.com/styled-components/jest-styled-components#theming

推荐的解决方案是将主题作为道具传递： const wrapper = shallow(<Button theme={theme} />)

所以我将以下代码添加到我的LooksBrowser 测试文件中：

const theme = {
  LooksBrowser: {
    SlideTitle: {
      FontFamily: 'Futura-Light, sans-serif'
    },
    SlideSubtitle: {
      FontFamily: 'Futura-Demi, sans-serif'
    }
  }
};

并编辑我的所有测试以手动通过主题。例如：

test('Compare snapshots', () => {
  const Component = renderer.create(<LooksBrowser theme={theme} currentSlide={{ imageURL: 'http://localhost:3001/img/D1_VW_SPW.jpg', index: 1, subtitle: 'Where amazing happens', title: 'The United States of America', textColor: '#fff' }} nextSlide={{ imageURL: '', index: 0, subtitle: '', title: '', textColor: '' }} />);

  const Tree = Component.toJSON();
  expect(Tree).toMatchSnapshot();
});

完成此操作后，我再次运行测试。还是会出现同样的错误。

解决方案二

我决定将我的组件包装在 Styled Components ThemeProvider 中。这修复了我的 Compare snapshots 和 Renders without crashing 测试中的错误。

但是，由于我还要更改我的 LooksBrowser 组件的道具/状态并测试结果，所以这不再起作用。这是因为setProps 和setState 函数只能在根/包装器组件上使用。

因此，将我的组件包装在 ThemeProvider 组件中也不是一个有效的解决方案。

解决方案三

我决定尝试记录我的一个 Styled Components 的 props。所以我将我的SlideTitle 子组件更改为：

const SlideTitle = styled.p`
  flex: 0 0 auto;
  text-transform: uppercase;
  line-height: 1;
  color: ${props => {
    console.log(props.theme.LooksBrowser.SlideTitle.FontFamily);
    return props.color;
  }};
  font-family: ${props => props.theme.LooksBrowser.SlideTitle.FontFamily};
  font-size: ${PXToVW(52)};
`;

我收到以下错误：

TypeError: Cannot read property 'SlideTitle' of undefined

  44 |   line-height: 1;
  45 |   color: ${props => {
> 46 |     console.log(props.theme.LooksBrowser.SlideTitle.FontFamily);
  47 |     return props.color;
  48 |   }};
  49 |   font-family: ${props => props.theme.LooksBrowser.SlideTitle.FontFamily};

好吧，好像整个主题道具都是空的。让我们尝试手动将主题传递给SlideTitle（顺便说一句，这是一个可怕的解决方案，这意味着我需要手动将主题传递给整个项目中的每个样式化组件）。

所以我添加了以下代码：

<SlideTitle theme={this.props.theme} color{this.state.currentSlide.textColor}>{this.state.currentSlide.title}</SlideTitle>

然后我再次运行我的测试。我在终端中看到以下行：

console.log src/app/components/LooksBrowser/LooksBrowser.js:46
Futura-Light, sans-serif

是的，这就是我要找的！我向下滚动并再次看到相同的错误... yikes。

解决方案四

在Jest Styled Components documentation我也看到了如下解决方案：

const shallowWithTheme = (tree, theme) => {
  const context = shallow(<ThemeProvider theme={theme} />)
    .instance()
    .getChildContext()
  return shallow(tree, { context })
}

const wrapper = shallowWithTheme(<Button />, theme)

好的，看起来很有希望。所以我将此函数添加到我的测试文件中并将我的Check if componentDidUpdate gets called 测试更新为：

test('Check if componentDidUpdate gets called', () => {
  const spy = jest.spyOn(LooksBrowser.prototype, 'componentDidUpdate');
  const Component = shallowWithTheme(<LooksBrowser currentSlide={{ imageURL: 'http://localhost:3001/img/D1_VW_SPW.jpg', index: 1, subtitle: 'Where amazing happens', title: 'The United States of America', textColor: '#fff' }} nextSlide={{ imageURL: '', index: 0, subtitle: '', title: '', textColor: '' }} />, Theme);

  Component.setProps({ nextSlide: { imageURL: 'http://localhost:3001/img/D2_VW_SPW.jpg', index: 2, subtitle: 'Don\'t walk here at night', title: 'What A View', textColor: '#fff' } });
  expect(spy).toBeCalled();
});

我运行测试并得到以下错误：

Error
Cannot tween a null target. thrown

有道理，因为我使用的是shallow。所以我将函数更改为使用mount 而不是浅：

const shallowWithTheme = (tree, theme) => {
  const context = mount(<ThemeProvider theme={theme} />)
    .instance()
    .getChildContext()
  return mount(tree, { context })
}

我再次运行测试，瞧：

TypeError: Cannot read property 'SlideTitle' of undefined

我正式没有想法。

如果有人对此有任何想法，将不胜感激！提前谢谢大家。

编辑

我现在还在 Github 上开了两期，一期在 Styled Components repo，一期在 Jest Styled Components repo。

到目前为止，我已经尝试了那里提供的所有解决方案，但均无济于事。因此，如果这里有人对如何解决此问题有任何想法，请分享！

【问题讨论】：

标签： javascript reactjs jestjs enzyme styled-components

【解决方案1】：

将ThemeProvider 包裹在组件周围并将theme 对象传递给它，对我来说很好。

import React from 'react';
import { ThemeProvider } from 'styled-components';
import { render, cleanup } from '@testing-library/react';

import Home from '../Home';
import { themelight } from '../../Layout/theme';

afterEach(cleanup);

test('home renders correctly', () => {
  let { getByText } = render(
    <ThemeProvider theme={themelight}>
      <Home name={name} />
    </ThemeProvider>
  );

  getByText('ANURAG HAZRA');
})

【讨论】：

这对我有用！唯一的区别是我有一个更复杂的 ThemeProvider 设置 (gist.github.com/eyerean/84210966cc8822d88260c3c08c891981)，但我仍然可以用它在我的测试中包装组件并且测试通过了。

【解决方案2】：

在一位同事的帮助下，我设法解决了这个问题。我有另一个组件扩展了 SlideTitle 组件，它破坏了测试：

const SlideSubtitle = SlideTitle.extend`
  font-family: ${props => 
  props.theme.LooksBrowser.SlideSubtitle.FontFamily};
`;

我将我的代码重构为：

const SlideTitlesSharedStyling = styled.p`
  flex: 0 0 auto;
  text-transform: uppercase;
  line-height: 1;
  color: ${props => props.color};
  font-size: ${PXToVW(52)};
`;

const SlideTitle = SlideTitlesSharedStyling.extend`
  font-family: ${props => props.theme.LooksBrowser.SlideTitle.FontFamily};
`;

const SlideSubtitle = SlideTitlesSharedStyling.extend`
  font-family: ${props => props.theme.LooksBrowser.SlideSubtitle.FontFamily};
`;

我的测试又开始通过了！

【讨论】：