mocking jest后恢复实现

Question

我正在尝试模拟一个函数，并在测试之后将真正的实现用于其他测试。

const myService = () => {
    return {
      foo: () => return 1;
    }
}

const myService = require('./myService.js');

jest.mock('./myService');

describe('testing myService', () => {
  it('should return 2 by mocked', () => {
    myService.mockImplementation(() => ({
      foo: jest.fn().mockResolvedValueOnce(2),
    }));
    expect.assertions(1);
    expect(myService().foo()).toBe(2);
    jest.restoreAllMocks();
  });
  it('should return 1', () => {
    expect(myService().foo()).toBe(1);
  });
});

但是在这之后，foo()仍然被嘲笑。

Answer 1

jest.spyOn(object, methodName)是为对象创建模拟方法的更好选择。

我们可以通过在afterEach()钩子中使用jest.restoreAllMocks()来将该方法恢复到原始实现。

请注意，仅当使用jest.spyOn创建模拟时，jest.restoreAllMocks()才有效；其他模拟将需要您手动恢复它们。

例如。

myService.js

const myService = () => {
  return {
    foo: () => 1,
  };
};
module.exports = myService;

myService.test.js

const myService = require('./myService.js');

describe('testing myService', () => {
  afterEach(() => {
    jest.restoreAllMocks();
  });
  it('should return 2 by mocked', () => {
    const service = myService();
    jest.spyOn(service, 'foo').mockReturnValueOnce(2);
    expect(service.foo()).toBe(2);
    expect(service.foo).toBeCalledTimes(1);
  });
  it('should return 1', () => {
    const service = myService();
    expect(jest.isMockFunction(service.foo)).toBeFalsy();
    expect(service.foo()).toBe(1);
  });
});

测试结果：

 PASS  examples/68459394/myService.test.js (8.465 s)
  testing myService
    ✓ should return 2 by mocked (3 ms)
    ✓ should return 1

Test Suites: 1 passed, 1 total
Tests:       2 passed, 2 total
Snapshots:   0 total
Time:        9.548 s