CODEWITHSUNDEEP
angularunit-testingtestingrxjsobservable
Hubert Kubiak
Hubert Kubiak

Reputation: 635

How to test an observable stream?

I want to write unit tests in Angular for the following function:

exportToCsv(query: string) {
    this.exportToCsvService.exportDataAndGetCsv(query).pipe(
      first(),
      tap(response => this.fireCsvDownload(response))
    ).subscribe();
  }

The function exportDataAndGetCsv makes a http call and returns a string. I think the test I would write should check if the fireCsvDownload was executed. I tried:

it('should fire fireCsvDownload after exporting data and geting csv ', () => {
    component.exportToCsv(query);
    fixture.detectChanges();
    expect(component.fireCsvDownload).toHaveBeenCalled();
  });

But I get an error: Error: <toHaveBeenCalled> : Expected a spy, but got Function. What should I do? I provide the exportToCsv service to the TestBed and the exportDataAndGetCsv returns of('text').

Upvotes: 0

Views: 400

Answers (1)

Chrillewoodz
Chrillewoodz

Reputation: 28368

Create a spy which you replace in the expect:

it('should fire fireCsvDownload after exporting data and geting csv ', () => {

    const mySpy = spyOn(component, 'fireCsvDownload');
    component.exportToCsv(query);
    fixture.detectChanges();
    expect(mySpy).toHaveBeenCalled();
  });

You might have to do:

const mySpy = spyOn(component, 'fireCsvDownload').and.callThrough();

But I'm not certain without testing myself.

Upvotes: 2

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