@Test
  void emptyIterable() {
    check(criteria.list.isEmpty()).matches("{list: []}");
    check(criteria.list.notEmpty()).matches("{$and: [{list: {$exists: true}}, {list:{$ne:null}}, {list: {$ne:[]}}]}");
  }
{@code in} / {@code notIn} with single element converted to {@code eq} / {@code ne}
criteria/mongo/test/org/immutables/criteria/mongo/FindVisitorTest.java