React测试库:测试属性/属性 [英] React testing library: Test attribute / prop

问题描述

我正在使用TypeScript编写React应用.我将material-ui用于组件，将react-testing-library用于单元测试.

I'm writing a React app using TypeScript. I use material-ui for my components and react-testing-library for my unit tests.

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.

I'm writing a wrapper for material-ui's Grid component so that I always have an item.

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);

我想编写一个检查item={true}是否可用的单元测试.我试图像这样使用帮助程序库jest-dom的toHaveAttribute:

I want to write a unit test that checks if item={true}. I tried to use the helper library jest-dom's toHaveAttribute like this:

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");
    });
  });
});

但是此测试失败并显示:

But this test fails with:

● 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?

How can I test if an element has a certain attribute?

推荐答案

jest-dom toHaveAttribute断言在测试尝试测试item prop <时断言item 属性 /em>.

jest-dom toHaveAttribute assertion asserts item attribute while the test tries to test item prop.

item道具不一定会导致item属性，并且由于它是非标准属性，因此很可能不会.

item prop won't necessarily result in item attribute, and since it's non-standard attribute it most probably won't.

react-testing-library传播功能测试并声明结果DOM，这需要了解组件的工作方式.可以看到

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.

除了已测试的单元外，所有单元都应在单元测试中进行模拟，例如:

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}/>
}));

然后可以将其声明为:

  expect(getByTestId("grid-item")).toHaveClass("item");

这篇关于React测试库:测试属性/属性的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！