Some pieces can be tested using public APIs

public class PlayerFrameTest extends TestCase {
    
    private JFrame frame;
    private JMenuBar menubar;

    protected void setUp() throws QTException {
        frame = new PlayerFrame();
        menubar = frame.getJMenuBar();
    }

    public void testTitleOfUntitledFrameIsAmateurPlayer()
      throws QTException {
        assertEquals("Amateur Player", frame.getTitle());
    }
    
    public void testInitialFrameIsNotTooSmall() throws QTException { 
        Dimension d = frame.getSize();
        assertTrue(d.width > 300);
        assertTrue(d.height > 300);
    }
    
}