@Test
  void one() {
    Assertions.assertThrows(NonUniqueResultException.class, () -> {
      // empty
      Flowable.fromPublisher(create().one()).toList().blockingGet();
    });

    // one
    check(Flowable.fromPublisher(create("one").one()).toList().blockingGet()).hasContentInAnyOrder("one");

    Assertions.assertThrows(NonUniqueResultException.class, () -> {
      // two
      Flowable.fromPublisher(create("one", "two").one()).toList().blockingGet();
    });
  }
Check that correct exceptions are thrown by {@link ReactiveFetcher}
criteria/common/test/org/immutables/criteria/repository/reactive/ReactiveFetcherDelegateTest.java