public static String validateIndexName(@Nullable String indexName) {
    checkDbIdentifier(indexName, "Index name", INDEX_NAME_MAX_SIZE);
    return indexName;
  }
@Test
  public void validateIndexName_throws_NPE_when_index_name_is_null() {
    assertThatThrownBy(() -> validateIndexName(null))
      .isInstanceOf(NullPointerException.class)
      .hasMessage("Index name can't be null");
  }