为什么在 JEST 测试中 getComputedStyle() 会为 Chrome / Firefox DevTools 中的计算样式返回不同的结果

Question

我已经MyStyledButton基于material-ui 编写了一个自定义按钮 ( ) Button。

import React from "react";
import { Button } from "@material-ui/core";
import { makeStyles } from "@material-ui/styles";

const useStyles = makeStyles({
  root: {
    minWidth: 100
  }
});

function MyStyledButton(props) {
  const buttonStyle = useStyles(props);
  const { children, width, ...others } = props;

  return (

      <Button classes={{ root: buttonStyle.root }} {...others}>
        {children}
      </Button>
     );
}

export default MyStyledButton;

它使用主题进行样式设置，这指定backgroundColor为黄色阴影（特别是#fbb900）

import { createMuiTheme } from "@material-ui/core/styles";

export const myYellow = "#FBB900";

export const theme = createMuiTheme({
  overrides: {
    MuiButton: {
      containedPrimary: {
        color: "black",
        backgroundColor: myYellow
      }
    }
  }
});

该组件在 my main 中实例化index.js并包装在theme.

  <MuiThemeProvider theme={theme}>
     <MyStyledButton variant="contained" color="primary">
       Primary Click Me
     </MyStyledButton>
  </MuiThemeProvider>

如果我检查 Chrome DevTools 中的按钮，它background-color会按预期“计算”。在 Firefox DevTools 中也是如此。

但是，当我编写一个 JEST 测试来检查background-color并查询按钮的 DOM 节点样式时，getComputedStyles()我transparent回来了，但测试失败了。

const wrapper = mount(
    <MyStyledButton variant="contained" color="primary">
      Primary
    </MyStyledButton>
  );
  const foundButton = wrapper.find("button");
  expect(foundButton).toHaveLength(1);
  //I want to check the background colour of the button here
  //I've tried getComputedStyle() but it returns 'transparent' instead of #FBB900
  expect(
    window
      .getComputedStyle(foundButton.getDOMNode())
      .getPropertyValue("background-color")
  ).toEqual(myYellow);

我已经包含了一个带有确切问题的 CodeSandbox，要重现的最少代码和失败的 JEST 测试。

Answer 1

我已经接近了，但还没有找到解决方案。

主要问题是 MUIButton 向元素注入一个标签来支持样式。这在您的单元测试中不会发生。我能够通过使用材质测试使用的createMount来使其工作。

修复后，样式可以正确显示。然而，计算的样式仍然不起作用。看起来其他人已经遇到了酶正确处理这个问题的问题 - 所以我不确定这是否可能。

要达到我所在的位置，请获取您的测试片段，将其复制到顶部，然后将测试代码更改为：

const myMount = createMount({ strict: true });
  const wrapper = myMount(
    <MuiThemeProvider theme={theme}>
      <MyStyledButton variant="contained" color="primary">
        Primary
      </MyStyledButton>
    </MuiThemeProvider>
  );

class Mode extends React.Component {
  static propTypes = {
    /**
     * this is essentially children. However we can't use children because then
     * using `wrapper.setProps({ children })` would work differently if this component
     * would be the root.
     */
    __element: PropTypes.element.isRequired,
    __strict: PropTypes.bool.isRequired,
  };

  render() {
    // Excess props will come from e.g. enzyme setProps
    const { __element, __strict, ...other } = this.props;
    const Component = __strict ? React.StrictMode : React.Fragment;

    return <Component>{React.cloneElement(__element, other)}</Component>;
  }
}

// Generate an enhanced mount function.
function createMount(options = {}) {

  const attachTo = document.createElement('div');
  attachTo.className = 'app';
  attachTo.setAttribute('id', 'app');
  document.body.insertBefore(attachTo, document.body.firstChild);

  const mountWithContext = function mountWithContext(node, localOptions = {}) {
    const strict = true;
    const disableUnnmount = false;
    const localEnzymeOptions = {};
    const globalEnzymeOptions = {};

    if (!disableUnnmount) {
      ReactDOM.unmountComponentAtNode(attachTo);
    }

    // some tests require that no other components are in the tree
    // e.g. when doing .instance(), .state() etc.
    return mount(strict == null ? node : <Mode __element={node} __strict={Boolean(strict)} />, {
      attachTo,
      ...globalEnzymeOptions,
      ...localEnzymeOptions,
    });
  };

  mountWithContext.attachTo = attachTo;
  mountWithContext.cleanUp = () => {
    ReactDOM.unmountComponentAtNode(attachTo);
    attachTo.parentElement.removeChild(attachTo);
  };

  return mountWithContext;
}