### Question:
OF13MatchSerializer implements OFSerializer<Match>, SerializerRegistryInjector { public void serializeMatchEntries(List<MatchEntry> matchEntries, ByteBuf out) { if (matchEntries == null) { LOG.debug("Match entries are null"); return; } for (MatchEntry entry : matchEntries) { MatchEntrySerializerKey<?, ?> key = new MatchEntrySerializerKey<>( EncodeConstants.OF13_VERSION_ID, entry.getOxmClass(), entry.getOxmMatchField()); if (entry.getOxmClass().equals(ExperimenterClass.class)) { ExperimenterIdCase entryValue = (ExperimenterIdCase) entry.getMatchEntryValue(); key.setExperimenterId(entryValue.getExperimenter().getExperimenter().getValue()); } else { key.setExperimenterId(null); } OFSerializer<MatchEntry> entrySerializer = registry.getSerializer(key); entrySerializer.serialize(entry, out); } }  @Override void serialize(Match match, ByteBuf outBuffer); void serializeMatchEntries(List<MatchEntry> matchEntries, ByteBuf out); @Override void injectSerializerRegistry(SerializerRegistry serializerRegistry);  }### Answer:
@Test(expected=IllegalStateException.class) public void testSerializeExperimenterMatchEntry() { List<MatchEntry> entries = new ArrayList<>(); MatchEntryBuilder builder = new MatchEntryBuilder(); builder.setOxmClass(ExperimenterClass.class); builder.setOxmMatchField(OxmMatchFieldClass.class); builder.setHasMask(true); ExperimenterIdCaseBuilder caseBuilder = new ExperimenterIdCaseBuilder(); ExperimenterBuilder expBuilder = new ExperimenterBuilder(); expBuilder.setExperimenter(new ExperimenterId(42L)); caseBuilder.setExperimenter(expBuilder.build()); builder.setMatchEntryValue(caseBuilder.build()); entries.add(builder.build()); ByteBuf out = UnpooledByteBufAllocator.DEFAULT.buffer(); ((OF13MatchSerializer) matchSerializer).serializeMatchEntries(entries, out); }