final ObjectDiffer objectDiffer = ObjectDifferBuilder.buildDefault();
final DiffNode node = objectDiffer.compare(modifiedPhoneBook, phoneBook);
assertThat(node.hasChanges(), is(true));
assertThat(node.hasChildren(), is(true));
assertThat(node.childCount(), is(1));
final DiffNode contactsNode = node.getChild("contacts");
assertThat(contactsNode, IsNull.notNullValue());
assertThat(contactsNode.hasChanges(), is(true));