code: function() {
        if (window.getAngularTestability) {
          if (rootSelector) {
            var testability = null;
            var el = document.querySelector(rootSelector);
            try{
              testability = window.getAngularTestability(el);
            }
            catch(e){}
            if (testability) {
              testability.whenStable(testCallback);
              return;
            }
          }
  
          // Didn't specify root element or testability could not be found
          // by rootSelector. This may happen in a hybrid app, which could have
          // more than one root.
          var testabilities = window.getAllAngularTestabilities();
          var count = testabilities.length;
  
          // No angular2 testability, this happens when
          // going to a hybrid page and going back to a pure angular1 page
          if (count === 0) {
            testCallback();
            return;
          }
  
          var decrement = function() {
            count--;
            if (count === 0) {
              testCallback();
            }
          };
          testabilities.forEach(function(testability) {
            testability.whenStable(decrement);
          });
  
        }
        else {testCallback();}  // not an angular2 app
      }
docs: Wait for Angular2 testability and then run test callback