How to check multiple arguments on multiple calls for jest spies?

Question

I have the following function in a React component:

onUploadStart(file, xhr, formData) {
  formData.append('filename', file.name);
  formData.append('mimeType', file.type);
}

This is my test that at least gets the spy to be called:

const formData = { append: jest.fn() };
const file = { name: 'someFileName', type: 'someMimeType' };
eventHandlers.onUploadStart(file, null, formData);

expect(formData.append).toHaveBeenCalledWith(
  ['mimeType', 'someMimeType'],
  ['fileName', 'someFileName']
);

However, the assertion is not working:

Expected mock function to have been called with:
 [["mimeType", "someMimeType"], ["fileName", "someFileName"]]
But it was called with:
  ["mimeType", "someMimeType"], ["filename", "someFileName"]

What is the right way to use toHaveBeenCalledWith?

Solution 1

I was able mock multiple calls and check the arguments this way:

expect(mockFn.mock.calls).toEqual([
  [arg1, arg2, ...], // First call
  [arg1, arg2, ...]  // Second call
]);

where mockFn is your mocked function name.

Solution 2

Since jest 23.0 there is .toHaveBeenNthCalledWith(nthCall, arg1, arg2, ....) https://jestjs.io/docs/expect#tohavebeennthcalledwithnthcall-arg1-arg2-

Also under the alias: .nthCalledWith(nthCall, arg1, arg2, ...)

If you have a mock function, you can use .toHaveBeenNthCalledWith to test what arguments it was nth called with. For example, let's say you have a drinkEach(drink, Array<flavor>) function that applies f to a bunch of flavors, and you want to ensure that when you call it, the first flavor it operates on is 'lemon' and the second one is 'octopus'. You can write:

test('drinkEach drinks each drink', () => {
  const drink = jest.fn();
  drinkEach(drink, ['lemon', 'octopus']);
  expect(drink).toHaveBeenNthCalledWith(1, 'lemon');
  expect(drink).toHaveBeenNthCalledWith(2, 'octopus');
});

Note: the nth argument must be positive integer starting from 1.

Solution 3

You can also test toHaveBeenCalledWith and test multiple times for each expected parameter combination.

One example is Google Analytics plugin api uses the same function call with different parameter combinations.

function requireGoogleAnalyticsPlugins() {
  ...
  ga('create', 'UA-XXXXX-Y', 'auto');
  ga('require', 'localHitSender', {path: '/log', debug: true});
  ga('send', 'pageview');
}

To test this the below example tests that ga has been called three times with the various parameter combinations.

describe("requireGoogleAnalyticsPlugins", () => {
  it("requires plugins", () => {
    requireGoogleAnalyticsPlugins();
    expect(GoogleAnalytics.ga.toHaveBeenCalledTimes(3);
    expect(GoogleAnalytics.ga).toHaveBeenCalledWith('create', 'UA-XXXXX-Y', 'auto');
    expect(GoogleAnalytics.ga).toHaveBeenCalledWith('require', 'localHitSender', {path: '/log', debug: true});
    expect(GoogleAnalytics.ga).toHaveBeenCalledWith('send', 'pageview');
  });
});

In OP case you could test this with

expect(formData.append).toHaveBeenCalledWith('mimeType', 'someMimeType');
expect(formData.append).toHaveBeenCalledWith('fileName', 'someFileName');

Solution 4

The signature is .toHaveBeenCalledWith(arg1, arg2, ...), where arg1, arg2, ... means in a single call (see).

If you want to test multiple calls, just expect it multiple times.

Unfortunately, I have not yet found a method to test the order of multiple calls.

Solution 5

You can also create an array of the expected arguments per call and loop over it:

const expectedArgs = ['a', 'b', 'c', 'd']
expectedArgs.forEach((arg, index) => 
    expect(myFunc).toHaveBeenNthCalledWith(index + 1, arg))

This solution considers the order of the calls. If you do not care about the order, you can use toHaveBeenCalledWith without the index instead.

View more solutions

Comments

[Andi]

I believe I've addressed how to use a single expect (see my answer below).

[Toni Feistauer]

this should be the "best answer"

[WhatsThePoint]

While this link may assist in your answer to the question, you can improve this answer by taking vital parts of the link and putting it into your answer, this makes sure your answer is still an answer if the link gets changed or removed :)

[rubmz]

This method does not work/supported - unfortunately!

[quirimmo]

Even if not provided an example in the answer, this point is really valid! up to yoU!

[Andi]

@IlyaSaunkin <3

[Jacob Raihle]

This checks the order of the calls, not just that they have all happened (which may or may not be desired). But toHaveBeenNthCalledWith wants 1 if it is checking the first call, not 0, so the index is off by one.

[Kim Kern]

@JacobRaihle Thanks for pointing that out. :) I have updated the answer according to your comment.

[Hew Wolff]

Also, note that if you don't know exactly what the parameters should be, you can use things like expect.objectContaining.