discourse/test/javascripts/views/header-view-test.js.es6

moduleFor("view:header");

test("showNotifications", function() {
  var controllerSpy = {
    send: sinon.spy()
  };
  var view = this.subject({controller: controllerSpy});
  view.showNotifications();

  ok(controllerSpy.send.calledWith("showNotifications", view), "sends showNotifications message to the controller, passing header view as a param");
});