javascript - 如何使用 jest 进入 setTimeout 函数

Question

使用 Jest 和 Enzyme，如何运行 setTimeout() 内的代码？我还希望延迟时间被视为 0，这样就不会延迟我的测试

正在测试的功能:

   functionToBeTested = () => {
           //more code...
            setTimeout(() => {
              console.log('not logging :/')
              return 'anything';
            }, 1000);
    }

测试:

it('functionToBeTested', () => { 
    expect(functionToBeTested).toEqual('anything');
}) 

Answer 1

这是单元测试解决方案:

index.ts:

export const functionToBeTested = () => {
  return new Promise(resolve => {
    setTimeout(() => {
      console.log('not logging :/');
      resolve('anything');
    }, 1000);
  });
};

index.spec.ts:

import { functionToBeTested } from './';

jest.useFakeTimers();

test('should return correctly', async () => {
  const logSpy = jest.spyOn(console, 'log');
  const promise = functionToBeTested();
  jest.runAllTimers();
  await expect(promise).resolves.toBe('anything');
  expect(logSpy).toBeCalledWith('not logging :/');
});

100%覆盖率的单元测试结果:

 PASS  src/stackoverflow/56942805/index.spec.ts (8.036s)
  ✓ should return correctly (10ms)

  console.log node_modules/jest-mock/build/index.js:860
    not logging :/

----------|----------|----------|----------|----------|-------------------|
File      |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
----------|----------|----------|----------|----------|-------------------|
All files |      100 |      100 |      100 |      100 |                   |
 index.ts |      100 |      100 |      100 |      100 |                   |
----------|----------|----------|----------|----------|-------------------|
Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        9.608s

源代码:https://github.com/mrdulin/jest-codelab/tree/master/src/stackoverflow/56942805