Android ActivityInstrumentationTestCase2 how to test multiplie activites

im trying to understand how to work with tests. Not good but for one activity with simple controls i create test , and it's going very well.

Than i start to try with 2 or more activities and i stuck here . From one activity after some controls click i going to other activity (it's how in app ) but how to do it in tests i can find . For getting controls from first activity i write

MyFirstTestActivity mftActivity;
....
super(MyFirstTestActivity.class);
mftActivity = getActivity();

and i can easy work with controls from first activity, but how to get other activities ? After click on last button in first activity, i make delay and other activity showed for me , but i cant test there anything. Please help someone if any one know, documentation not tell me nothing about it , and i googlin full day and not find anything