Jest：尽管期望/接收值不匹配，但异步测试错误地通过

Question

Jest 中的以下测试不应通过：const targetFile = require("../targetFile.js");fetch = jest.fn(() => Promise.resolve('file scoped default value'));test('diffFileFetch', () => {  fetch.mockImplementation(() => new Promise((resolve, reject) => {    resolve('wrong value');  }));  targetFile.diffFileFetch()    .then(async data => {      await expect(data).toEqual('correct value');    })    .catch(e => console.log(e, `=====e=====`));});catch 块触发但测试仍然通过。这是什么原因，应该如何解决？PASS  views/admin/__tests__/CurrentCouponListingSection.test.js  ✓ diffFileFetch (6ms) console.log views/admin/__tests__/testFile.test.js:59    { Error: expect(received).toEqual(expected) // deep equality    Expected: "correct value"    Received: "wrong value"        at targetFile.diffFileFetch.then (/var/www/html/wptest2/wp-content/plugins/fvc/views/admin/__tests__/testFile.test.js:58:1)        at <anonymous>        at process._tickCallback (internal/process/next_tick.js:188:7)      matcherResult:        { actual: 'wrong value',         expected: 'correct value',         message: [Function],         name: 'toEqual',         pass: false } } '=====e====='也试过从 .then() 中删除 async/await。没有不同。

Answer 1

测试在Promise回调运行之前完成，所以它通过了......然后错误被记录下来。

如果测试包含异步代码，则您需要使用done：

test('diffFileFetch', done => {  // <= use done

  fetch.mockImplementation(() => new Promise((resolve, reject) => {

    resolve('wrong value');

  }));

  targetFile.diffFileFetch()

    .then(data => {

      expect(data).toBe('correct value');

      done();  // <= now call done

    })

});

...返回Promise：

test('diffFileFetch', () => {

  fetch.mockImplementation(() => new Promise((resolve, reject) => {

    resolve('wrong value');

  }));

  return targetFile.diffFileFetch()  // <= return the Promise

    .then(data => {

      expect(data).toBe('correct value');

    })

});

...或者使用async测试功能和await在Promise：

test('diffFileFetch', async () => {  // <= async test function

  fetch.mockImplementation(() => new Promise((resolve, reject) => {

    resolve('wrong value');

  }));

  const data = await targetFile.diffFileFetch()  // <= await the Promise

  expect(data).toBe('correct value');

});