CODEWITHSUNDEEP
javascriptpromisemockingjestjs
Hommer Smith
Hommer Smith

Reputation: 27862

Test failing after adding then and catch to promise

I have the following (simplified for the sake of scoping down problem) code:

function pushPromises() {
  const promises = [];

  promises.push(firstPromise('something'))
  promises.push(secondPromise('somethingelse'))

  return promises;
}

export default handlePromises(async (c) => {
  const results = await Promise.all(pushPromises())
  c.success(results);
});

My test mocks those firstPromise and secondPromise to check if they were called with the right arguments. This works (assume mock set up is properly done):

jest.mock('src/firstPromise');
jest.mock('src/secondPromise');

describe('test', () => {
  let firstMock;
  let secondMock;


  beforeEach(() => {
    require('src/firstPromise').default = firstMock;
    require('src/secondPromise').default = secondMock;
  })

  it('test', async () => {
    await handlePromises(context);
    expect(firstPromiseMock).toHaveBeenCalledTimes(1);
    expect(secondPromiseMock).toHaveBeenCalledTimes(1);
  });
});

Now, if I add handlers to the promises such as:

function pushPromises() {
      const promises = [];

      promises.push(
        firstPromise('something')
        .then(r => console.log(r))
        .catch(e => console.log(e))
      )
      promises.push(
        secondPromise('somethingelse')
        .then(r => console.log(r))
        .catch(e => console.log(e))
      )

      return promises;
    }

The first expectation passes, but the second one doesn't. It looks like the second promise is no longer called.

How can I modify the test/code so that adding handlers on the promises don't make the test break? It looks like it is just finishing the execution on the first promise handler and does never get to the second one.

EDIT:

I have modified the function to return a Promise.all without await:

 export default handlePromises(async (c) => {
      return Promise.all(pushPromises())
 });

But I'm having the exact same issue. The second promise is not called if the first one has a .then.

Upvotes: 0

Views: 142

Answers (2)

arizafar
arizafar

Reputation: 3132

Your handlePromises function accepts a callback but you are handling it as it returns a promise, it is not a good way to go but you can test your method using callback as following

Modify your Test as=>

it('test', (done) => {
    handlePromises(context);
    context.success = (results) => {
        console.log(results)
        expect(firstPromiseMock).toHaveBeenCalledTimes(1);
        expect(secondPromiseMock).toHaveBeenCalledTimes(1);
        done();
    }
});

Or modify your code as =>

function pushPromises() {
  const promises = [];

  promises.push(firstPromise('something'))
  promises.push(secondPromise('somethingelse'))

  return promises;
}

export default handlePromises = (context) => {
  return Promise.all(pushPromises()).then((data) => context.success(data))
};

//with async
export default handlePromises = async (context) => {
  let data = await Promise.all(pushPromises());
  context.success(data)
};

Upvotes: 0

Keith
Keith

Reputation: 24241

In your edit, your handlePromises is still not a promise..

Try the following. ->

it('test', async () => {
  await Promise.all(pushPromises());
  expect(firstPromiseMock).toHaveBeenCalledTimes(1);
  expect(secondPromiseMock).toHaveBeenCalledTimes(1);
});

Upvotes: 1

Related Questions