transformer.transform(protocol, dom);
// In actual operation this transformer would form a compound
// transformer with the NullRemovingDOMTransformer.
NullRemovingDOMTransformer nullRemover = new NullRemovingDOMTransformer();
nullRemover.transform(null, dom);
String domAsString = helper.render(dom);
String expectedAsString = helper.render(expected);
assertEquals("DOM comparison failed", expectedAsString, domAsString);