### Question:
WindowClassAdapter implements GriffonPivotAdapter, org.apache.pivot.wtk.WindowClassListener { public void activeWindowChanged(org.apache.pivot.wtk.Window arg0) { if (activeWindowChanged != null) { activeWindowChanged.call(arg0); } }  CallableWithArgs<Void> getActiveWindowChanged(); void setActiveWindowChanged(CallableWithArgs<Void> activeWindowChanged); void activeWindowChanged(org.apache.pivot.wtk.Window arg0);  }### Answer:
@Test public void testActiveWindowChanged() { final boolean[] invoked = new boolean[1]; CallableWithArgs<Void> callable = new CallableWithArgs<Void>() { public Void call(Object... args) { invoked[0] = true; return null; } }; assertNull(adapter.getActiveWindowChanged()); adapter.activeWindowChanged(null); assertFalse(invoked[0]); adapter.setActiveWindowChanged(callable); adapter.activeWindowChanged(null); assertTrue(invoked[0]); }