public static List<List<byte[]>> generateMessages(@NonNull final List<Integer> messageCountList) throws FileNotFoundException { final Schema schema = getSchema("test_schema"); final TestKafkaSchemaService schemaService = new TestKafkaSchemaService(); final ISchemaService.ISchemaServiceWriter writer = schemaService.getWriter("test_schema", 1); final List<List<byte[]>> ret = new ArrayList<>(messageCountList.size()); messageCountList.stream().forEach( messageCount -> { ret.add(KafkaTestHelper.getTestData(schema, messageCount).stream().map( record -> { try { return writer.write(record); } catch (InvalidDataException e) { throw new RuntimeException(e); } } ).collect(Collectors.toList())); } ); return ret; }