List<RecordAndMetadata> fullRecords() {
            return Collections.unmodifiableList(
                records
                    .stream()
                    .sorted(Comparator.comparingLong(record -> record.offset))
                    .collect(Collectors.toList())
            );
        }
A simple Coordinator implementation that stores the records into a set.
group-coordinator/src/test/java/org/apache/kafka/coordinator/group/runtime/CoordinatorRuntimeTest.java