Covering unit test for array with .find method in angular using karma and jasmine

Question

Trouble covering the following piece of code in spec file using karma and jasmine in angular 8

myMethod(id: number): boolean {
  const data= this.myService.getSampleData();
  return data.find(item => item.id === id).count;
}

spec:

it('should call myMethod ', () => {
    spyOn(myService,'getSampleData').and.returnValue(of([{id:1,count:10}]))
    component.myMethod(1);
});

It throws cannot read property .find of undefined. Although i tried spyOn(myService,'getSampleData').and.returnValue(of([{id:1,count:10}])) moving into beforeEach function as well but no luck

Answer 1

your method expects to get an array of items. however you return Observable < Array< Item>> from your spy. try this spyOn(myService,'getSampleData').and.returnValue([{id:1,count:10}])

Answer 2

The first issue is that you are returning an Observable using of when the Service seems to return an array of items.

Second, you are not doing any expect to validate something in the test.

I would do this:

it('should call myMethod ', () => {
    spyOn(myService,'getSampleData').and.returnValue([{id:1, count:10}]);
    expect(component.myMethod(1)).toEqual(true);
});