public void testAddMutator() { setUpTest(); c.setMutator( new CompositeCollection.CollectionMutator() { public boolean add(CompositeCollection composite, Collection[] collections, Object obj) { for (int i = 0; i < collections.length; i++) { collections[i].add(obj); } return true; } public boolean addAll( CompositeCollection composite, Collection[] collections, Collection coll) { for (int i = 0; i < collections.length; i++) { collections[i].addAll(coll); } return true; } public boolean remove( CompositeCollection composite, Collection[] collections, Object obj) { return false; } }); c.addComposited(one); c.add("foo"); assertTrue(c.contains("foo")); assertTrue(one.contains("foo")); }