Using object types with Jasmine's toHaveBeenCalledWith method

Question

I've just started using Jasmine so please forgive the newbie question but is it possible to test for object types when using toHaveBeenCalledWith?

expect(object.method).toHaveBeenCalledWith(instanceof String);

I know I could this but it's checking the return value rather than the argument.

expect(k instanceof namespace.Klass).toBeTruthy();

Solution 1

toHaveBeenCalledWith is a method of a spy. So you can only call them on spy like described in the docs:

// your class to test
var Klass = function () {
};

Klass.prototype.method = function (arg) {
  return arg;
};


//the test
describe("spy behavior", function() {

  it('should spy on an instance method of a Klass', function() {
    // create a new instance
    var obj = new Klass();
    //spy on the method
    spyOn(obj, 'method');
    //call the method with some arguments
    obj.method('foo argument');
    //test the method was called with the arguments
    expect(obj.method).toHaveBeenCalledWith('foo argument');   
    //test that the instance of the last called argument is string 
    expect(obj.method.calls.mostRecent().args[0] instanceof String).toBeTruthy();
  });

});

Solution 2

I've discovered an even cooler mechanism, using jasmine.any(), as I find taking the arguments apart by hand to be sub-optimal for legibility.

In CoffeeScript:

obj = {}
obj.method = (arg1, arg2) ->

describe "callback", ->

   it "should be called with 'world' as second argument", ->
     spyOn(obj, 'method')
     obj.method('hello', 'world')
     expect(obj.method).toHaveBeenCalledWith(jasmine.any(String), 'world')

Comments

[stefan.s]

jasmine.any(Function) is handy, too

[jds]

Andreas, is there any reason you added .toBeTruthy()? It seems like that is unnecessary.

[fncomp]

Noticed that it also works inside on references. for example: expect(obj.method).toHaveBeenCalledWith({done: jasmine.any(Function)}). Very useful.

[Mark Amery]

@gwg expect(foo) without a matcher is a no-op; the line would do nothing without the toBeTruthy() call. See jsfiddle.net/2doafezv/2 for proof.

[Mark Amery]

This is out of date; obj.method.mostRecentCall needs to become obj.method.calls.mostRecent() in Jasmine 2.0. Also, using jasmine.any(), as described in the other answer, is clearer and cuter. Finally, this answer takes a while to get to the point; essentially everything you wrote besides expect(obj.method.mostRecentCall.args[0] instanceof String).toBeTruthy(); isn't really needed to explain yourself.

[Fagner Brack]

As of the time of this writing, Jasmine does not check for the same instance of new String('world') when using toHaveBeenCalledWith(...arguments). Click here to understand why that is important.

[Admin]

Had to check if a callback function was called, jasmin.any(Function) saved my life, thank you