javascript / intermediate
Snippet
Mocking Dependencies with Jasmine Spies
When testing Angular components, you should isolate them by mocking their dependencies. Jasmine 'spies' allow you to track calls to a function and define what it should return, preventing actual HTTP calls or side effects during tests.
snippet.js
javascript
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it('should fetch data on init', () => {const service = TestBed.inject(DataService);const spy = spyOn(service, 'getData').and.returnValue(of(['Item 1']));component.ngOnInit();expect(spy).toHaveBeenCalled();expect(component.items).toEqual(['Item 1']);});
angular
Breakdown
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spyOn(service, 'getData')
Creates a wrapper around the service method to intercept its execution.
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and.returnValue(of(['Item 1']))
Forces the spy to return a mock Observable instead of executing the original logic.