Testing buttons in PlayMode Tests

In my Scene I have a Button and I want to test that the Event visible in the Inspector will be triggered and execute the correct action. In this case I have a setup Button and I want to test that the Setup Dialog appears which will be true if the dialog will be found by FindObject because it will be activated by the event handler specified in the Inspector. This is my test:

 [UnityTest]
 public IEnumerator SetupButtonTestSetupButton()
 {
     yield return PlayModeSetup();
     yield return null;
     var Settings_UI = GameObject.Find("Settings_UI");
     Assert.Null(Settings_UI);
     var setupButton = Object.FindObjectOfType<Button>();
     Assert.NotNull(setupButton);
     clicked = false;
     setupButton.onClick.AddListener(Clicked);
     setupButton.onClick.Invoke();
     //ExecuteEvents.Execute(setupButton.gameObject, new PointerEventData(EventSystem.current), ExecuteEvents.pointerClickHandler);
     Assert.True(clicked);
     yield return null;
     yield return new WaitForSeconds(1);
     Settings_UI = GameObject.Find("Settings_UI");
     Assert.NotNull(Settings_UI);
     var Settings_UITransform = Settings_UI.transform;
     Assert.NotNull(Settings_UITransform);
     Assert.True(Settings_UI.activeSelf);
 }
 
 private void Clicked()
 {
     clicked = true;
 }

Running my test an Exception is thrown at

 Assert.NotNull(Settings_UI);

That means that my Listener in the test was called but not the event specified in the Inspector. If I use the mouse to click the Button during WaitForSeconds the test goes green. How can I make the test go green by script? Thanks, Wolfgang