Any way to modify Jasmine spies based on arguments?

Solution 1:

In Jasmine versions 3.0 and above you can use withArgs

describe('my fn', function() {
  it('gets user name and ID', function() {
    spyOn(externalApi, 'get')
      .withArgs('abc').and.returnValue('Jane')
      .withArgs('123').and.returnValue(98765);
  });
});

For Jasmine versions earlier than 3.0 callFake is the right way to go, but you can simplify it using an object to hold the return values

describe('my fn', function() {
  var params = {
    'abc': 'Jane', 
    '123': 98765
  }

  it('gets user name and ID', function() {
    spyOn(externalApi, 'get').and.callFake(function(myParam) {
     return params[myParam]
    });
  });
});

Depending on the version of Jasmine, the syntax is slightly different:

• 1.3.1: .andCallFake(fn)
• 2.0: .and.callFake(fn)

Resources:

• withArgs docs
• callFake docs
• andCallFake vs and.callFake

Solution 2:

You could also use $provide to create a spy. And mock using and.returnValues instead of and.returnValue to pass in parameterised data.

As per Jasmine docs: By chaining the spy with and.returnValues, all calls to the function will return specific values in order until it reaches the end of the return values list, at which point it will return undefined for all subsequent calls.

describe('my fn', () => {
    beforeEach(module($provide => {
        $provide.value('externalApi', jasmine.createSpyObj('externalApi', ['get']));
    }));

        it('get userName and Id', inject((externalApi) => {
            // Given
            externalApi.get.and.returnValues('abc','123');

            // When
            //insert your condition

            // Then
            // insert the expectation                
        }));
});