@SuppressWarnings("unchecked")
        @Override
        public com.yahoo.processing.Response process(com.yahoo.processing.Request request, Execution execution) {
            try {
                com.yahoo.processing.Response response = execution.process(request);
                response.data().add(new ProcessorLibrary.StringData(request, stringDataPrefix + "d1"));
                freeze.get();
                response.data().freeze();
                // wait for permission from test driver to add more data
                addLastData.get();
                response.data().add(new ProcessorLibrary.StringData(request, stringDataPrefix + "d2"));
                return response;
            }
            catch (InterruptedException | ConcurrentModificationException | ExecutionException e) {
                throw new RuntimeException(e);
            }
        }
Tests that the ResponseStatus takes precedence over errors
container-core/src/test/java/com/yahoo/processing/handler/ProcessingHandlerTestCase.java