### Question:
MainActivity extends AppCompatActivity implements ActivityCallback { @Override public void showProgressBar() { progressBar.setVisibility(View.VISIBLE); }  @Override void startRepoInfoFragment(Repository repository); @Override void showProgressBar(); @Override void hideProgressBar();  }### Answer:
@Test public void testShowProgressBar() throws Exception { mainActivity.showProgressBar(); verify(progressBar).setVisibility(View.VISIBLE); }