public TopicName createTopic(String topicName) {
    checkArgument(!topicName.isEmpty(), "topicName can not be empty");
    checkIsUsable();

    TopicName name = getTopicName(topicName);
    return createTopicInternal(name);
  }
@Test
  public void testCreateTopicWithInvalidNameShouldFail() {
    IllegalArgumentException exception =
        assertThrows(IllegalArgumentException.class, () -> testManager.createTopic(""));
    assertThat(exception).hasMessageThat().contains("topicName can not be empty");
  }