### Question:
ButtonAdapter implements GriffonPivotAdapter, org.apache.pivot.wtk.ButtonListener { public void buttonGroupChanged(org.apache.pivot.wtk.Button arg0, org.apache.pivot.wtk.ButtonGroup arg1) { if (buttonGroupChanged != null) { buttonGroupChanged.call(arg0, arg1); } }  CallableWithArgs<Void> getButtonDataChanged(); CallableWithArgs<Void> getDataRendererChanged(); CallableWithArgs<Void> getActionChanged(); CallableWithArgs<Void> getToggleButtonChanged(); CallableWithArgs<Void> getTriStateChanged(); CallableWithArgs<Void> getButtonGroupChanged(); void setButtonDataChanged(CallableWithArgs<Void> buttonDataChanged); void setDataRendererChanged(CallableWithArgs<Void> dataRendererChanged); void setActionChanged(CallableWithArgs<Void> actionChanged); void setToggleButtonChanged(CallableWithArgs<Void> toggleButtonChanged); void setTriStateChanged(CallableWithArgs<Void> triStateChanged); void setButtonGroupChanged(CallableWithArgs<Void> buttonGroupChanged); void buttonDataChanged(org.apache.pivot.wtk.Button arg0, java.lang.Object arg1); void dataRendererChanged(org.apache.pivot.wtk.Button arg0, org.apache.pivot.wtk.Button.DataRenderer arg1); void actionChanged(org.apache.pivot.wtk.Button arg0, org.apache.pivot.wtk.Action arg1); void toggleButtonChanged(org.apache.pivot.wtk.Button arg0); void triStateChanged(org.apache.pivot.wtk.Button arg0); void buttonGroupChanged(org.apache.pivot.wtk.Button arg0, org.apache.pivot.wtk.ButtonGroup arg1);  }### Answer:
@Test public void testButtonGroupChanged() { final boolean[] invoked = new boolean[1]; CallableWithArgs<Void> callable = new CallableWithArgs<Void>() { public Void call(Object... args) { invoked[0] = true; return null; } }; assertNull(adapter.getButtonGroupChanged()); adapter.buttonGroupChanged(null, null); assertFalse(invoked[0]); adapter.setButtonGroupChanged(callable); adapter.buttonGroupChanged(null, null); assertTrue(invoked[0]); }