parent.addDerived( designElement );
CoreTestUtil.addDerived( parent, designElement );
	public void testAddDerived( )	{		TextItem parent = new TextItem( );		parent.setName( "parent" ); //$NON-NLS-1$		designElement.setExtendsElement( parent );		Object o = parent.getDescendents( ).get( 0 );		assertEquals( designElement, o );		// drop parent		parent.dropDerived( designElement );		assertFalse( parent.getDescendents( ).contains( designElement ) );		// add parent		parent.addDerived( designElement );		assertTrue( parent.getDescendents( ).contains( designElement ) );	}