Jasmine - Spying on a method call within a constructor

javascript testing jasmine spy
Levi McCallum picture Levi McCallum · Jan 4, 2012 · Viewed 27.3k times · Source

I want to test whether the following method is called with in my Javascript object constructor. From what I have seen in the Jasmine documentation, I can spy on a constructor method and I can spy on methods after an object has been instantiated, but I can't seem to be able to spy on a method before the object is constructed.

The object:

Klass = function() {
    this.called_method();
};

Klass.prototype.called_method = function() {
  //method to be called in the constructor.
}

I want to do something like this in the spec:

it('should spy on a method call within the constructor', function() {
    spyOn(window, 'Klass');
    var obj = new Klass();
    expect(window.Klass.called_method).toHaveBeenCalled();
});

Answer

Dave Newton picture Dave Newton · Jan 4, 2012

Spy directly on the prototype method:

describe("The Klass constructor", function() {
  it("should call its prototype's called_method", function() {
      spyOn(Klass.prototype, 'called_method');  //.andCallThrough();
      var k = new Klass();
      expect(Klass.prototype.called_method).toHaveBeenCalled();
  });
});

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