@Test
  public void empty() throws Exception {
    check(repository.findAll().fetchAll().getUnchecked()).isEmpty();
    check(repository.findAll().fetchFirst().getUnchecked()).isAbsent();
    check(repository.findById("").fetchAll().getUnchecked()).isEmpty();
    check(repository.findById("MISSING").fetchAll().getUnchecked()).isEmpty();
  }
Basic CRUD operations on the top of repository
mongo/test/org/immutables/mongo/fixture/BasicMongoOperationsTest.java