使用 react-testing-library 测试 useEffect 内部的 api 调用 [英] Testing api call inside useEffect using react-testing-library

问题描述

我想测试 api 调用和返回的数据，这些数据应该显示在我的功能组件中.我创建了执行 api 调用的 List 组件.我希望返回的数据显示在组件中，为此我使用了 useState 钩子.组件如下所示:

const 列表:FC<{}>= () =>{const [data, setData] = useState();const getData = (): Promise=>{return fetch('https://jsonplaceholder.typicode.com/todos/1');};React.useEffect(() => {const func = async() =>{const 数据 = 等待 getData();const value = await data.json();设置数据(值.标题)；}功能()；}, [])返回 (<div><div id="test">{data}</div>

)}

我写了一个测试，其中我模拟了 fetch 方法.我检查 fetch 方法是否已被调用并且它确实发生了.不幸的是，我不知道如何测试响应返回的值.当我尝试 console.log 时，我只是得到 null，我想得到示例文本".我的猜测是我必须等待从 Promise 返回的这个值.不幸的是，尽管尝试使用行为和等待方法，但我不知道如何实现它.这是我的测试:

it('test', async() => {让组件；const fakeResponse = '示例文本';const mockFetch = Promise.resolve({json: () => Promise.resolve(fakeResponse)});const mockedFetch = jest.spyOn(window, 'fetch').mockImplementationOnce(() => mockFetch as any )等待等待(异步()=> {组件 = 渲染(<列表/>)；})const 值:Element = component.container.querySelector('#test');console.log(value.textContent);期望(mockedFetch).toHaveBeenCalledTimes(1);})

如果您有任何建议，我将不胜感激.

第二次尝试

也尝试使用 data-testid="test" 和 waitForElement，但仍然收到空值.

更新的组件增量:

 const 列表:FC<{}>= () =>{- const [data, setData] = useState();+ const [data, setData] = useState('test');const getData = (): Promise=>{return fetch('https://jsonplaceholder.typicode.com/todos/1');};React.useEffect(() => {const func = async() =>{const 数据 = 等待 getData();const value = await data.json();setData(value.title);}功能()；}, [])返回 (<div>- <div id="test">{data}</div>+ 
)}

和更新的测试:

it('test', async() => {const fakeResponse = '示例文本';const mockFetch = Promise.resolve({json: () => Promise.resolve(fakeResponse)});const mockedFetch = jest.spyOn(window, 'fetch').mockImplementationOnce(() => mockFetch as any )const { getByTestId } = render(<List/>);expect(getByTestId("test")).toHaveTextContent("test");const resolveValue = await waitForElement(() => getByTestId('test'));expect(resolvedValue).toHaveTextContent(示例文本");期望(mockedFetch).toHaveBeenCalledTimes(1);})

解决方案

这是一个工作单元测试示例:

index.tsx:

import React, { useState, FC } from 'react';导出常量列表:FC<{}>= () =>{const [data, setData] = useState();const getData = (): Promise=>{return fetch('https://jsonplaceholder.typicode.com/todos/1');};React.useEffect(() => {const func = async() =>{const 数据 = 等待 getData();const value = await data.json();设置数据(值.标题)；};功能()；}, []);返回 (<div><div data-testid="test">{data}</div>

);};

index.test.tsx:

import { List } from './';从反应"导入反应；导入'@testing-library/jest-dom/extend-expect';从'@testing-library/react'导入{渲染，waitForElement}；描述('59892259'，()=> {让 originFetch;beforeEach(() => {originFetch = (全局为任何).fetch;});afterEach(() => {(全局为任何).fetch = originFetch;});it('应该通过', async() => {const fakeResponse = { title: '示例文本' };const mRes = { json: jest.fn().mockResolvedValueOnce(fakeResponse) };const mockedFetch = jest.fn().mockResolvedValueOnce(mRes as any);(全局为任何).fetch = mockedFetch;const { getByTestId } = render(<List></List>);const div = await waitForElement(() => getByTestId('test'));期望(div).toHaveTextContent('示例文本');期望(mockedFetch).toBeCalledTimes(1);期望(mRes.json).toBeCalledTimes(1);});});

单元测试结果:

 PASS src/stackoverflow/59892259/index.test.tsx (9.816s)59892259✓ 应该通过 (63ms)-----------|----------|----------|----------|----------|--------------------|档案 |% stmts |% 分支 |% 函数 |% 行 |未覆盖的行#s |-----------|----------|----------|----------|----------|--------------------|所有文件 |100 |100 |100 |100 ||index.tsx |100 |100 |100 |100 ||-----------|----------|----------|----------|----------|--------------------|测试套件:1 次通过，总共 1 次测试:1 次通过，共 1 次快照:共 0 个时间:11.73s，估计13s

I want to test api call and data returned which should be displayed inside my functional component. I created List component which performs api call. I would like the returned data to be displayed in the component and I use the useState hook for this. Component looks like this:

const List: FC<{}> = () => {
    const [data, setData] = useState<number>();
    const getData = (): Promise<any> => {
        return fetch('https://jsonplaceholder.typicode.com/todos/1');
    };

    React.useEffect(() => {
        const func = async () => {
            const data = await getData();
            const value = await data.json();
            setData(value.title);
        }
        func();
    }, [])

    return (
        <div>
            <div id="test">{data}</div>
        </div>
    )
}

I wrote one test in which I mocked the fetch method. I check if the fetch method has been called and it actually happens. Unfortunately, I don't know how I could test the value returned from response. When I try console.log I just get null and I'd like to get 'example text'. My guess is that I have to wait for this value returned from Promise. Unfortunately, despite trying with methods act and wait, I don't know how to achieve it. Here is my test:

it('test', async () => {
    let component;
    const fakeResponse = 'example text';
    const mockFetch = Promise.resolve({json: () => Promise.resolve(fakeResponse)});
    const mockedFetch = jest.spyOn(window, 'fetch').mockImplementationOnce(() => mockFetch as any )
    await wait( async () => {
        component = render(<List />);
    })
    const value: Element = component.container.querySelector('#test');
    console.log(value.textContent);
    expect(mockedFetch).toHaveBeenCalledTimes(1);
})

I would be really thankful for any suggestions.

Second Attempt

Also tried using data-testid="test" and waitForElement, but still receiving null value.

updated component deltas:

  const List: FC<{}> = () => {
-     const [data, setData] = useState<number>();
+     const [data, setData] = useState<string>('test');
      const getData = (): Promise<any> => {
          return fetch('https://jsonplaceholder.typicode.com/todos/1');
      };
  
      React.useEffect(() => {
          const func = async () => {
              const data = await getData();
              const value = await data.json();
              setData(value.title);
          }
          func();
      }, [])
  
      return (
          <div>
-             <div id="test">{data}</div>
+             <div data-testid="test" id="test">{data}</div>
          </div>
      )
  }

and updated test:

it('test', async () => {
    const fakeResponse = 'example text';
    const mockFetch = Promise.resolve({json: () => Promise.resolve(fakeResponse)});
    const mockedFetch = jest.spyOn(window, 'fetch').mockImplementationOnce(() => mockFetch as any )
    const { getByTestId } = render(<List />);
    expect(getByTestId("test")).toHaveTextContent("test");
    const resolvedValue = await waitForElement(() => getByTestId('test'));
    expect(resolvedValue).toHaveTextContent("example text");
    expect(mockedFetch).toHaveBeenCalledTimes(1);
})

解决方案

Here is a working unit testing example:

index.tsx:

import React, { useState, FC } from 'react';

export const List: FC<{}> = () => {
  const [data, setData] = useState<number>();
  const getData = (): Promise<any> => {
    return fetch('https://jsonplaceholder.typicode.com/todos/1');
  };

  React.useEffect(() => {
    const func = async () => {
      const data = await getData();
      const value = await data.json();
      setData(value.title);
    };
    func();
  }, []);

  return (
    <div>
      <div data-testid="test">{data}</div>
    </div>
  );
};

index.test.tsx:

import { List } from './';
import React from 'react';
import '@testing-library/jest-dom/extend-expect';
import { render, waitForElement } from '@testing-library/react';

describe('59892259', () => {
  let originFetch;
  beforeEach(() => {
    originFetch = (global as any).fetch;
  });
  afterEach(() => {
    (global as any).fetch = originFetch;
  });
  it('should pass', async () => {
    const fakeResponse = { title: 'example text' };
    const mRes = { json: jest.fn().mockResolvedValueOnce(fakeResponse) };
    const mockedFetch = jest.fn().mockResolvedValueOnce(mRes as any);
    (global as any).fetch = mockedFetch;
    const { getByTestId } = render(<List></List>);
    const div = await waitForElement(() => getByTestId('test'));
    expect(div).toHaveTextContent('example text');
    expect(mockedFetch).toBeCalledTimes(1);
    expect(mRes.json).toBeCalledTimes(1);
  });
});

unit test result:

 PASS  src/stackoverflow/59892259/index.test.tsx (9.816s)
  59892259
    ✓ should pass (63ms)

-----------|----------|----------|----------|----------|-------------------|
File       |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
-----------|----------|----------|----------|----------|-------------------|
All files  |      100 |      100 |      100 |      100 |                   |
 index.tsx |      100 |      100 |      100 |      100 |                   |
-----------|----------|----------|----------|----------|-------------------|
Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        11.73s, estimated 13s

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