assertTrue("not null", manager1 != null);
DesktopManager manager2 = ui.getDesktopManager();
assertTrue("the same object", manager1 == manager2);
assertNull("no desktop pane", frame.getDesktopPane());
// the desktop pane is set
JDesktopPane desktop = new JDesktopPane();
desktop.add(frame);
manager2 = ui.getDesktopManager();
assertTrue("not null", manager2 != null);
assertTrue("is taken from desktop pane", manager2 == frame.getDesktopPane()
.getDesktopManager());
assertTrue("another object", manager2 != manager1);