Issue with getting unit test to pass involving DOM

I am not sure why the DOM element that I try to create in my unit test always return either undefined or null. I need the DOM element to attach the event listener to it. I am using Mocha and Chai to do my client side Javascript testing.

I have written the following test:

  it('should change the isClick value when a click event occurs', function() {
      let target = document.createElement('span');
      let isClick = false;

      testFunction(target, isClick);
      target.dispatchEvent(new Event("click")); // code here does not work since target is either undefined or null

      chai.assert.isTrue(isClick, "isClick should now be true");
    });

The testFunction looks like this:

    function testFunction(target, isClick) {
      target.addEventListener("click", (e) => {
         isClick = !isClick;
      });
    }

I am not sure if I am suppose to create a spy or stub for the DOM element, can someone give me pointers on how I should approach a test case like this?