how to spyon same method but two different parameters in jest?

user_3659052 0
Viewed 8397
    jest
      .spyOn(webService.prototype, 'isEnabled')
      .mockImplementation(() => {
        return Promise.resolve(true)
      })
    jest
      .spyOn(webService.prototype, 'isEnabled')
      .mockImplementation(() => {
        return Promise.resolve(false)
      })

So what I want is to return 'true' if parameter has 'YES' string in it. and return 'false' if parameter has 'NO' in it.

the typescript of function is like below..

  public isEnabled(featureId: string): Promise<boolean> {
    return this.toggle.isEnabled(featureId)
  }
nestjs jestjs typescript
2 Answers

jonrsharpe has the right idea in the comments. You can add a mock implementation to your spy and do something like

jest.spyOn(webService.prototype, 'isEnabled')
  .mockImplementation((yesOrNo: string) => {
    if (yesOrNo.includes('YES')) {
      return true;
    } else {
      return false;
    }
  });

And now it works for both the YES and NO parameter. Of course you can add on and tailor the logic more to your needs.

user_95761860

In addition to the last answer, I would create a utility function for mocking that method, this way you can initializate and clear this after each test execution, something like:

util:

const webServiceMock = {
  init(isEnabled) {
    jest.spyOn(webService.prototype, 'isEnabled')
      .mockImplementation(() => isEnabled);
  },
  destroy() {
    jest.clearAllMocks();
  }
};

tests:

describe('webService', () => {
  afterEach(() => {
    webServiceMock.destroy();
  });

  test('is enabled', () => {
    webServiceMock.init(true);
    expect(webService.isEnabled()).toBe(true);
  });

  test('is disabled', () => {
    webServiceMock.init(false);
    expect(webService.isEnabled()).toBe(false);
  });
});
user_149545030
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