@Test
  void lowerCaseIndexName() {
    check(IndexResolver.defaultResolver().resolve(getClass())).is(getClass().getSimpleName().toLowerCase());
  }
From ES <a href="https://www.elastic.co/guide/en/elasticsearch/guide/current/_document_metadata.html#_index">docs</a>:
This name must be lowercase, cannot begin with an underscore, and cannot contain commas.
criteria/elasticsearch/test/org/immutables/criteria/elasticsearch/IndexResolverTest.java