how to get arguments on an event emitter in jasmine test

Question

I have a unit test as below

it('billing information is correct', () => {
    fixture.detectChanges();
    spyOn(component.myEventEmitter, 'emit').and.callThrough();
    component.form.controls['size'].setValue(12);
    fixture.detectChanges();
    **let args= component.myEventEmitter.emit.mostRecentCall **
    expect(args.billingSize).toEqual('30')
});

When size changes, myEventEmitter is being emitted with a large json object which includes billingSize. And I want the test to check if this value is as expected. But looks like I can't do 'mostRecentCall/ calls' on the event emitter. What can I try next?

Note: I don't want to do expect(component.myEventEmitter.emit).toHaveBeenCalledWith(*dataExpected*) because the dataExpected is a large JSON object. I just care about one field.

score 6 · Accepted Answer · answered Oct 25 '17 at 21:20

This should work.

it('billing information is correct', () => {
  fixture.detectChanges();
  spyOn(component.myEventEmitter, 'emit').and.callThrough();
  component.form.controls['size'].setValue(12);
  fixture.detectChanges();
  let arg: any = (component.myEventEmitter.emit as any).calls.mostRecent().args[0];
  expect(arg.billingSize).toEqual('30');
});

note:

 component.myEventEmitter.emit.calls.mostRecent()

- wouldn't compile (error: calls does not exist on type ..') so type it to 'any' and should work.

Alexey Kucherenko · Answer 2 · 2017-10-27T12:57:25.620

0

You can also use

 expect(component.myEventEmitter.emit).toHaveBeenCalledWith('eventName', 
  jasmine.objectContaining(*dataExpected*)
);

edited Oct 27 '17 at 12:57

answered Oct 27 '17 at 00:35

Alexey Kucherenko

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But looks like objectContaining expects the entire object. ( whole json object in my case). Can you provide an example? – Josf Oct 27 '17 at 01:16
@SoJosf You can take a look here https://github.com/robtweed/ewd-document-store/blob/master/spec/unit/proto/delete.spec.js#L52 I wrote these tests – Alexey Kucherenko Oct 27 '17 at 12:56
I have tried it. _expect(component.taskRowData.emit).toHaveBeenCalledWith(jasmine.objectContaining({ billingSize: 30 }));_ But think that is not quite useful in my case. The args in the eventEmitter looks like '{ taskRow: {'jsonobject'}, formValid: true}' The field I want to look for is inside 'jsonobject'. I got this error: _Expected spy emit to have been called with [ ] but actual calls were [ Object({ taskRow: Object({ id: 1, name: 'Test task', billable: false, billingSize: 30, billingPrice: 26.46_ ... – Josf Oct 29 '17 at 19:27
expect(component.taskRowData.emit).toHaveBeenCalledWith({ taskRow: jasmine.objectContaining({ billingSize: 30 }) }) ); – Alexey Kucherenko Oct 30 '17 at 15:10
Thanks Alexey for looking at this. But I am getting the same error with objectContaining. – Josf Oct 31 '17 at 03:04

how to get arguments on an event emitter in jasmine test

2 Answers2