如何在 describe 或 it 块中使用 jest.mock？

Question

我正在使用打字稿和玩笑。我有两个文件users.service.ts，它导入producer.ts。我想在 producer.ts 中模拟一个函数。这很好用

import { sendUserData } from './users.service';

const processDataSpy = jest.fn().mockImplementation(() => {
    throw new Error('failed');
  });

  jest.mock('../users/manager', () => ({
    sendEvent: async (arg1: string, arg2: string, arg3: any) =>
      processDataSpy(arg1, arg2, arg3),
  }));


describe('users.service', () => {

  it('invokes endpoint and returns proper data if unsuccessful', async () => {

    const result = await sendUserData(
      data
    );

    expect(result).toBe(false);

  });

但是，我想在 processDataSpy 中模拟不同的结果。我正在测试上面抛出错误的案例，但我想测试没有抛出错误的案例。如何测试多个案例？在我的“it”块中移动“jest.mock”会破坏测试......

  it('invokes endpoint and returns proper data if unsuccessful', async () => {
    
    jest.mock('../users/manager', () => ({
      sendEvent: async (arg1: string, arg2: string, arg3: any) =>
        processDataSpy(arg1, arg2, arg3),
    }));
    ...
    const result = await sendUserData(
      data
    );

    expect(result).toBe(false);

  });

我收到一条错误消息，表明不再使用或启动模拟。如何在“describe”或“it”块中使用“jest.mock”？

Answer 1

您可以在it 或test 块内使用processDataSpy.mockImplementation。

// Optionally reset the mock before each test
beforeEach(() => {
  processDataSpy.mockReset(); 
});

it('Another use case', async () => {
    
    processDataSpy.mockImplementation(() => {
      throw new Error('Another error');
    })
   
    const result = await sendUserData(
      data
    );

    expect(result).toBe(false);
});