@Test
public void nullKeyIsStored() throws Exception {

  try (KafkaStore<String, String> store = new KafkaStore<>(CLUSTER.bootstrapServers(), SERIALIZER, TOPIC)) {
    store.put(null, "value");
    assertThat(store.get(null), is("value"));
    assertThat(store.containsKey(null), is(true));
  }
}