如何测试使用自定义 TypeScript React Hook 的组件？

Question

我目前正在 Typescript 中编写一个 React 组件，它使用一个名为 useAxios 的 axios-hooks 钩子。这个钩子的一个使用例子是here:

 export const App = () => {
  const [{ data, loading, error }, refetch] = useAxios(
    "https://api.myjson.com/bins/820fc"
  );

  if (loading) return <p>Loading...</p>;
  if (error) return <p>Error!</p>;

  return (
    <div>
      <button onClick={e => refetch()}>refetch</button>
      <pre>{JSON.stringify(data, null, 2)}</pre>
    </div>
  );
};

const rootElement = document.getElementById("root");
render(<App />, rootElement);

我试图弄清楚如何编写一个可以模拟 useAxios 钩子的测试。我尝试创建底层 axios 组件的模拟，但无法正常工作：

import React from "react"
import { render } from "@testing-library/react"
import { Test } from "../test"
import useAxios from "axios-hooks"

jest.mock("axios-hooks")
const mockedAxios = useAxios as jest.Mocked<typeof useAxios>

it("Displays loading", () => {
  // How to mock the return values in the following line?
  // mockedAxios.

  const { getByText } = render(<Test />)

  expect(getByText("Loading...")).toBeDefined()
})

我知道我不应该模拟作为底层依赖项的 axios，我应该能够模拟 useAxios，但无论如何我都会尝试。

我意识到这个问题在 SO 上已经被多次提及，但我可以找到解决这个特定用例的方法。

非常感谢任何帮助！

Answer 1

模拟模块并为每个测试设置useAxios 的预期结果，例如

jest.mock('axios-hooks');

import useAxios from 'axios-hooks';

test('App displays loading when request is fetching', () => {
  useAxios.mockReturnValue(Promise.resolve({ loading: true }));
  // mount component
  // Verify "Loading" message is rendered
});

Answer 2

我自己想出了如何做到这一点。为了测试自定义钩子，我做了以下操作：

import * as useAxios from "axios-hooks"
jest.mock("axios-hooks")
const mockedAxios = useAxios as jest.Mocked<typeof useAxios>

it("Displays loading message", async () => {

  // Explicitly define what should be returned
  mockedAxios.default.mockImplementation(() => [
      {
        data: [],
        loading: true,
        error: undefined
      },
      () => undefined
    ])

  const { getByText } = render(<Test />)

  expect(getByText("Loading...")).toBeDefined()
})

Answer 3

为了让编译器对() => undefined 参数感到满意，我不得不跳过一些额外的环节。我不是双重as 的粉丝，但我不知道如何使它不那么冗长，因为我是 TS 新手。

import * as useAxios from 'axios-hooks';
import { AxiosPromise } from 'axios';
import React from 'react';
import Test from 'components/Test';
import { render } from '@testing-library/react';

jest.mock('axios-hooks');
const mockedUseAxios = useAxios as jest.Mocked<typeof useAxios>;

it('renders a loading message', async () => {
  mockedUseAxios.default.mockImplementation(() => [
    {
      data: [],
      loading: true,
      error: undefined,
    },
    (): AxiosPromise => (undefined as unknown) as AxiosPromise<unknown>,
  ]);

  const { getByText } = render(<Test />);

  expect(getByText('Loading...')).toBeDefined();
});