How to Unit Test if a fragment has loaded correctly

I am really new to the concept of Unit Testing in android and I am trying to test some functionality of my app. Basically what I want is to test if a fragment has loaded correctly. In my case in the activity where the fragments are crated I have 3 buttons. Each button calls a different fragment. So I want to know how to unit test this. I think if I perform on click test on each button but I don't know how to test if the fragment has loaded correctly or not.

This is my test code so far:

public class TestHomeFragments extends ActivityInstrumentationTestCase2<Home>
{
private Home activity;
private Zone zone;

//Public Constructor
public TestHomeFragments() {
    super(Home.class);
}

public void setUp() throws Exception
{
    super.setUp();
    setActivityInitialTouchMode(false);
    activity = getActivity();
}

private Fragment startFragment(Fragment fragment) {
    FragmentTransaction transaction = zone.getFragmentManager().beginTransaction();
    transaction.add(R.id.recyclerViewZone, fragment, "tag");
    transaction.commit();
    getInstrumentation().waitForIdleSync();
    Fragment frag = zone.getFragmentManager().findFragmentByTag("tag");
    return frag;
}

public void testFragment() {
    Fragment fragment = new Fragment() {
        //Override methods and add assertations here.
    };

    startFragment(fragment);
}
}