React 测试库：测试 children 是否正确传递/呈现

Question

我正在使用 TypeScript 编写 React 应用程序。我对我的组件使用 material-ui，对我的单元测试使用 react-testing-library。

我正在为 material-ui 的 Grid 组件编写一个包装器，以便我始终拥有一个容器。

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

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

export default withStyles(styles)(GridContainer);

我想编写一个测试来检查 children 是否正确呈现。这是我写的：

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

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

describe("GridContainer", () => {
  const props = createTestProps();
  const { getByTestId } = render(
    <GridContainer {...props}>
      <div data-testid="child" />
    </GridContainer>
  );
  const container = getByTestId("grid-container");
  describe("rendering", () => {
    test("it renders it's children", () => {
      expect(container.children.length).toBe(1);
      expect(getByTestId("child")).toBeDefined();
    });
  });
});

问题出在测试的第一部分，我在其中检查 children 遍的长度。但是 expect(getByTestId("child")).toBeDefined(); 失败了：

● GridContainer › rendering › it renders it's children

    Unable to find an element by: [data-testid="child"]

    <body />

      24 |     test("it renders it's children", () => {
      25 |       expect(container.children.length).toBe(1);
    > 26 |       expect(getByTestId("child")).toBeDefined();
         |              ^
      27 |     });
      28 |   });
      29 | });

      at getElementError (node_modules/dom-testing-library/dist/query-helpers.js:30:10)
      at getAllByTestId (node_modules/dom-testing-library/dist/queries.js:231:45)
      at firstResultOrNull (node_modules/dom-testing-library/dist/query-helpers.js:38:30)
      at getByTestId (node_modules/dom-testing-library/dist/queries.js:241:42)
      at Object.getByTestId (src/components/Grid/GridContainer/GridContainer.test.tsx:26:14)

难道不能在 render 函数中给一个元素一个 data-testid 吗？我如何测试 children 是否正确呈现？

编辑这是调试的输出：

● Console

    console.log node_modules/react-testing-library/dist/index.js:57
      <body>
        <div>
          <div
            class="MuiGrid-container-2 GridContainer-grid-1 "
            data-testid="grid-container"
          >
            <div
              data-testid="child"
            />
          </div>
        </div>
      </body>

Answer 1

问题是您在 describe 块中渲染一次。这可能与您的想法不符。 describe 块中不在 test（或其他 jest 函数，如 beforeEach）中的代码会被 Jest 提前获取运行。一般来说，你永远不想在 describe 块内但在 test （或其他开玩笑的函数）之外的任何代码。

您可以在 beforeEach 中渲染组件，或者在每个测试中调用渲染辅助函数。

我用上面的方法在这里分叉了你的沙箱，现在两个测试都通过了：https://codesandbox.io/s/v3wk1vlx3l

React 测试库：测试 children 是否正确传递/呈现

React Testing Library: Test if children are passed / rendered correctly

unit-testing

typescript

reactjs

jestjs

react-testing-library