jasmine: Is this the only difference between returnValue and callFake?
callFake(() => {...}) takes a call back function
- If we just want a return value when a service method is called then we can use any of
and.callFake
orand.returnValue
component file:
@Component(...)
export class DependencyComponent {
constructor(private service: RandomService){....}
.....
sampleMethod() {
return this.service.randomMethod();
}
.....
}
unit test case for above component:
it('test callFake vs returnValue', () => {
let randomService= new RandomService();
let component = new DependencyComponent(randomService);
spyOn(randomService, 'randomMethod').and.callFake(() => 4)
expect(component.sampleMethod()).toBe(4)
spyOn(randomService, 'randomMethod').and.returnValue(10);
expect(component.sampleMethod()).toBe(10)
})
in above case both the ways are correct.
- Suppose we are passing a parameter to service method to perform its logic then in that case we have to use
and.callFake((param) => {...})
. Hereparam
parameter will be the argument passed to the spied method.
component file:
@Component(...)
export class DependencyComponent {
constructor(private service: RandomService){....}
.....
sampleMethod(val) {
return this.service.randomMethod(val);
}
.....
}
unit test case for above component:
it('test callFake vs returnValue', () => {
let randomService= new RandomService();
let component = new DependencyComponent(randomService);
spyOn(randomService, 'randomMethod').and.callFake((param) => param+4)
expect(component.sampleMethod(4)).toBe(8);
expect(component.sampleMethod(12)).toBe(16)
})
when component.sampleMethod(4)
is executed it will call this.service.randomMethod(4)
. As randomMethod()
is being spied using and.callFake
therefore 4
will be passed as argument of call back function of and.callFake
.