Angular unit Testing spyOn().and.callthrough doesn't call actual funciton - angularjs

Question

I am new in unit testing with Jasmine in Angular.
I am currently testing a service that has a function called loadSomething(id) and I have added a console.info in it.
MY SERVICE:
function loadSomething(id)
{
console.info('this is a test message');
return (a promise from a POST request)
}
And this is my test (spec) file:
//verify that the load function exists
it('load snapshot',function(){
expect(MyService.loadSomething(108)); //statement 1
spyOn(MyService, 'loadSomething').and.callThrough(); //statement 2
});
So, I read online that the callthrough method of SpyOn calls the ACTUAL function.
However, when i run my test with the expect statement (statement 1) the console.info message is invoked (that works fine). On the other hand, when I comment out statement 1 and uncomment the SpyOn(statement 2) I do not get the console.info message anymore.
I would expect the exact opposite to happen.
Have I understood something wrong here?
(the rest of the code works fine, both the spec file and the actual service, I just don't really get this specific thing)

Answer 1

The SpyOn will help you to setup how the function should react when it's being called upon in your tests. Basically it's jasmines way of creating mocks.
In your case you have defined what the test should do when the service function is being called, which is callThrough.
The problem is that you also need to act on the service function (or the scope function which calls your service method) in order
to trigger the SpyOn which will callThrough
it('load snapshot',function(){
//setup
spyOn(MyService, 'loadSomething').and.callThrough(); //statement 2
//act
//either call the scope function which uses the service
//$scope.yourServiceCallFunction();
//or call the service function directly
MyService.loadSomething(1); //this will callThrough
});
Here's an simple test where we will mock the response of the SpyOn to a string
it('test loadSomething',function(){
//setup
spyOn(MyService, 'loadSomething').and.returnValue('Mocked');
//act
var val = MyService.loadSomething(1);
//check
expect(val).toEqual('Mocked');
});