@Override
  public Optional<Rule> findByUuid(String uuid) {
    ensureInitialized();

    return Optional.ofNullable(rulesByUuid.get(uuid));
  }
@Test
  public void findByUuid_returns_absent_if_rule_does_not_exist_in_DB() {
    Optional<Rule> rule = underTest.findByUuid(AC_RULE_UUID);

    assertThat(rule).isEmpty();
  }