Is using spyOn() without a method possible?

Question

I'm new to jasmine and spies thing, hope you could point to the right direction.

I have an event listener that i want to cover with unit test:

    var nextTurn = function() {
    continueButton.addEventListener("click", displayComputerSelection)
};

nextTurn();

The general idea is to spy the 'displayComputerSelection' function .

it ("should call fn displayComputerSelection on continueButton click", function(){ spyOn(displayComputerSelection); continueButton.click(); expect(displayComputerSelection).toHaveBeenCalled();

Since the basic structure of spies is spyOn(<object>, <methodName>) i get a response No method name supplied . I've tried experimenting with jasmine.createSpy but couldn't make it work. How would i substitute for the method that is expected?

score 1 · Answer 1 · answered Sep 21 '17 at 18:28

Your problem

In your scenario, the whole question is how or where is displayComputerSelection defined, because this func is what you want to replace with your spy.

jasmine.createSpy()

It is jasmine.createSpy() that you want. For instance, the following is an example for how you can use it - totally untested - no pun intended.

var objectToTest = {
  handler: function(func) {
    func();
  }
};

describe('.handler()', function() {
  it('should call the passed in function', function() {
    var func = jasmine.createSpy('someName');

    objectToTest.handler(func);

    expect(func.calls.count()).toBe(1);
    expect(func).toHaveBeenCalledWith();
  });
});

Many thanks ! `displayComputerSelection` is a global variable, so i found out i simply needed to use `window`as an object. So it worked this way: `spyOn(window, "displayComputerSelection");` — Liudas Belickas, Sep 24 '17 at 07:43

score 0 · Answer 2 · answered Sep 24 '17 at 07:48

The answer in my specific case was:

it ("should call displayComputerSelection on continueButton click", function(){
    spyOn(window, "displayComputerSelection");
    start(); //first create spies, and only then "load" event listeners
    continueButton.click();
    expect(window.displayComputerSelection).toHaveBeenCalled();
});

Browser seems to hook up global var/functions to the 'window' object, thus it is to be spied upon.

Is using spyOn() without a method possible?

2 Answers2