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jasmine spy failing when being consumed by a promise

// CODE

var catalogDOM = (function() {
  return {
    updateAvailabilityForItem: function(quant) {
      console.log(">>>> in updateAvailabilityForItem")
    },
    syncAvailability: function() {
      return new Promise(function(resolve, reject) {
        ...
      })
    }
  }
})();

$(document).on("click", ".item_info", function() {
  console.log(">> calling sync")
  catalogDOM.syncAvailability()
  .catch(function() {
    console.log(">>> caught")
    catalogDOM.updateAvailabilityForItem(0)
  })
})

// SPEC

describe("click on item_info", function() {
  beforeEach(function() {
    info_btn = affix(".item_info")

    spyOn(catalogDOM, "updateAvailabilityForItem")
    syncFunction = spyOn(catalogDOM, "syncAvailability")
    syncFunction.and.returnValue(new Promise(function(resolve, reject) {reject()}))
    info_btn.click()
  })
  it("should call updateAvailabiliytForItem", function() {
    expect(catalogDOM.updateAvailabilityForItem).toHaveBeenCalledWith(0)
  })
})

// CONSOLE OUTPUT

>> calling sync
>>> caught
>>>> in updateAvailabilityForItem

The above spec is failing, moreover, I can see via console, see messages above, that catalogDOM.updateAvailabilityForItem is actually being called through... is there something about the promise set up that negates the spy?

7 months ago · Juan Pablo Isaza

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Accepted Answer · 2022-07-03T20:24:27.042Z

The issue is that the promise is happening asynchronously (at a later point in time) and when you expect, it is too early.

For a quick unblock, you can wrap you expectation in a setTimeout which will lower the priority of what's happening in the setTimeout to after the promise but I am not sure if this is a good approach.

// add done to function argument
it("should call updateAvailabiliytForItem", function(done) {
    setTimeout(() => {
      expect(catalogDOM.updateAvailabilityForItem).toHaveBeenCalledWith(0);
      // call done to let Jasmine know your asynchronous work is done.
      done();
    }, 100);
  })

You can read more about testing asynchronous stuff in Jasmine here: https://jasmine.github.io/tutorials/async

I usually use async/await for asynchronous tasks.