assertFalse( children.retainAll( otherCollection ) );
assertFalse( children.isDirty() );
otherCollection = new ArrayList();
otherCollection.add( otherChild );
assertFalse( children.removeAll( otherCollection ) );
assertFalse( children.isDirty() );
children.clear();
session.delete( child );
assertTrue( children.isDirty() );