16

我正在使用 TypeScript 编写一个 React 应用程序。我将 material-ui 用于我的组件，将 react-testing-library 用于我的单元测试。

我正在为 material-ui 的 Grid 组件编写一个包装器，这样我总是有一个项目。

import Grid from "@material-ui/core/Grid";
import withStyles, { WithStyles } from "@material-ui/core/styles/withStyles";
import React, { PureComponent } from "react";
import styles from "./styles";

export interface OwnProps {
  className?: string;
}

export interface Props extends WithStyles<typeof styles>, OwnProps {}

export interface DefaultProps {
  className: string;
}

export class GridItem extends PureComponent<Props & DefaultProps> {
  static defaultProps: DefaultProps = {
    className: ""
  };

  render() {
    const { classes, children, className, ...rest } = this.props;
    return (
      <Grid
        data-testid="grid-item"
        item={true}
        {...rest}
        className={classes.grid + " " + className}
      >
        {children}
      </Grid>
    );
  }
}

export default withStyles(styles)(GridItem);

我想编写一个单元测试来检查item={true}. 我尝试toHaveAttribute像这样使用辅助库 jest-dom：

import "jest-dom/extend-expect";
import React from "react";
import { cleanup, render } from "react-testing-library";
import GridItem, { OwnProps } from "./GridItem";
afterEach(cleanup);

const createTestProps = (props?: object): OwnProps => ({
  ...props
});

describe("Parallax", () => {
  const props = createTestProps();
  const { getByTestId } = render(<GridItem {...props} />);
  describe("rendering", () => {
    test("it renders the image", () => {
      expect(getByTestId("grid-item")).toHaveAttribute("item", "true");
    });
  });
});

但是这个测试失败了：

● GridItem › rendering › it renders the image

    expect(element).toHaveAttribute("item", "true") // element.getAttribute("item") === "true"

    Expected the element to have attribute:
      item="true"
    Received:
      null

      14 |   describe("rendering", () => {
      15 |     test("it renders the image", () => {
    > 16 |       expect(getByTestId("grid-item")).toHaveAttribute("item", "true");
         |                                        ^
      17 |     });
      18 |   });
      19 | });

      at Object.toHaveAttribute (src/components/Grid/GridItem/GridItem.test.tsx:16:40)

Test Suites: 1 failed, 3 passed, 4 total
Tests:       1 failed, 3 passed, 4 total
Snapshots:   0 total
Time:        1.762s, estimated 2s
Ran all test suites related to changed files.

如何测试元素是否具有特定属性？

4

2 回答 2

13

jest-dom toHaveAttributeassertion在测试尝试测试prop时断言item 属性。item

itemprop 不一定会产生item属性，并且由于它是非标准属性，因此很可能不会。

react-testing-library propagates functional testing and asserts resulting DOM, this requires to be aware of how components work. As can be seen here, item props results in adding a class to grid element.

All units but tested one should be mocked in unit tests, e.g.:

...
import GridItem, { OwnProps } from "./GridItem";

jest.mock("@material-ui/core/Grid", () => ({
  default: props => <div data-testid="grid-item" className={props.item && item}/>
}));

Then it could be asserted as:

  expect(getByTestId("grid-item")).toHaveClass("item");
于 2018-11-03T17:46:10.180 回答
5

If someone is still having this issue I solved it this way:

it('Check if it is a materialUI Grid item', () => {
    //Rendering the component in a constant.
    const { container } = render(<YourComponent />); 
    //Accessing the grid wrapper. In this case by the attribute you provided.
    const grid = container.querySelector('[data-testid="grid-item"]'); 
    //What we are expecting the grid to have.  
    expect(grid).toHaveClass('MuiGrid-item');
})

Notes:

  1. I noticed that in the code item it's been declared as a string and not as a boolean: item='true', which will trigger a warning when you run the test. item={true} is the correct way of declaring it. Actually in material UI when you write item inside a grid its of course by default true, in my opinion is not necessary.
  2. item is a class inside material UI Grid as the previous answer correctly suggested. So by that the correct class name should be refered in this case is 'MuiGrid-item'.
于 2020-08-25T18:49:08.143 回答