Cannot read property 'subscribe' of undefined after running npm test (Angular 2 unit testing)
Assuming you have a service that has a method that returns an observable, say
class SomeService {
getData(): Observable<Data> {}
}
You could....
Create a spy1 where you return an object with a noop subscribe function.
let mockSomeService = {
getData: () => {}
}
TestBed.configureTestingModule({
providers: [
{ provide: SomeService, useValue: mockSomeService }
]
})
it('...', () => {
spyOn(mockSomeService, 'getData').and.returnValue({ subscribe: () => {} })
// do stuff
expect(mockSomService.getData).toHaveBeenCalled();
})
You could...
Return an actual observable in the spy
spyOn(mockSomeService, 'getData').and.returnValue(Observable.of(someData))
Maybe this will be preferred over the noop subscribe method, because if the call on the service is changing something in the component, this is something you probably will want to test
You could...
Do something like in this post.
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Aiguo
Updated on December 20, 2020Comments
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Aiguo over 3 years
I've created a testing (spec) file for a component I'm testing. But when I run the test, it gives me an error saying
Cannot read property 'subscribe' of undefined TypeError: Cannot read property 'subscribe' of undefined at ComponentUndertest.ngOnInit
which is obvious because I have subscribed to something in my ngOnInit() method, but can I ignore the subscription during the test? Or can I fake a subscription during testing? I have googled a lot about this issue but couldn't find anything related with angular2 testing. Thanks in advance.
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Gerard Simpson almost 7 yearsThank you! testing is really confusing to being with
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Krystian over 6 yearsYou can also move returnValue action to mock : let mockSomeService = { getData: () => { return {subscribe: () => {} } } }