private static void verifyProcessedMessagesFirstRun() {
    assertEquals(4, PROCESSED.size());
    assertEquals(1, PROCESSED.get(commitMessage(0, 0)).get());
    assertEquals(1, PROCESSED.get(noCommitMessage(0, 1)).get());
    assertEquals(1, PROCESSED.get(commitMessage(1, 0)).get());
    assertEquals(1, PROCESSED.get(noCommitMessage(1, 1)).get());
  }
Each partition should have seen two messages before shutting down.
samza-test/src/test/java/org/apache/samza/test/kafka/KafkaCheckpointManagerIntegrationTest.java