assertFalse( children.remove( otherChild ) );
assertFalse( children.isDirty() );
ArrayList otherCollection = new ArrayList();
otherCollection.add( child );
assertFalse( children.retainAll( otherCollection ) );
assertFalse( children.isDirty() );
otherCollection = new ArrayList();
otherCollection.add( otherChild );
assertFalse( children.removeAll( otherCollection ) );