How to spy on mocked fetch interceptor?

Given the following mock (which is amazing by the way):

  // Disable Fetch API from making real network requests
  // @see https://undici.nodejs.org/#/docs/api/MockAgent?id=mockagentdisablenetconnect
  const fetchMock = getMiniflareFetchMock();
  fetchMock.disableNetConnect();

  // Intercept calls to Discord's webhook API
  const origin = fetchMock.get('https://discord.com');
  origin.intercept({ method: 'POST', path: /api\/webhooks\/.*/ }).reply(200, 'Mocked response!');

  // Disable Fetch API from making real network requests
  // @see https://undici.nodejs.org/#/docs/api/MockAgent?id=mockagentdisablenetconnect
  const fetchMock = getMiniflareFetchMock();
  fetchMock.disableNetConnect();

  // Intercept calls to Discord's webhook API
  const origin = fetchMock.get('https://discord.com');
  origin.intercept({ method: 'POST', path: /api\/webhooks\/.*/ }).reply(200, 'Mocked response!');

How do I spy on it and then check how often it's called?

expect(spy).toHaveBeenCalledTimes(1)

expect(spy).toHaveBeenCalledTimes(1)

1 Reply

WebberOP•2y ago

I've also tried to look through the interceptors API, and this seems to be the closest thing to a spy that I could find, but it doesn't work that way.

    const interceptors = fetchMock.pendingInterceptors()[0];

    ... make a call ...

    console.log(interceptors.consumed); // false
    console.log(interceptors.timesInvoked); // 0

    const interceptors = fetchMock.pendingInterceptors()[0];

    ... make a call ...

    console.log(interceptors.consumed); // false
    console.log(interceptors.timesInvoked); // 0

Ah it's actually not that hard once you know it 🙂

    const fetchSpy = vi.spyOn(global, 'fetch');

    ... make a call ...

    expect(fetchSpy).toHaveBeenCalledTimes(1);
    fetchMock.assertNoPendingInterceptors();

    const fetchSpy = vi.spyOn(global, 'fetch');

    ... make a call ...

    expect(fetchSpy).toHaveBeenCalledTimes(1);
    fetchMock.assertNoPendingInterceptors();

Mocks + spy combinations are always tricky and really hard to find great examples for most of the time.

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How to spy on mocked fetch interceptor?