@Test
  public void testShouldValidationPassWhenAllRequiredPropertiesAreProvidedInTopologyConfiguration() throws Exception {
    // GIVEN
    // configuration from the blueprint / cluster creation template
    topologyConfigurationMap.put("kerberos-env", new HashMap<>());
    topologyConfigurationMap.get("kerberos-env").put("realm", "etwas");
    topologyConfigurationMap.get("kerberos-env").put("kdc_type", "value");

    topologyConfigurationMap.put("krb5-conf", new HashMap<>());
    topologyConfigurationMap.get("krb5-conf").put("domains", "smthg");

    replayAll();

    // WHEN
    testSubject.validate(clusterTopologyMock);

    // THEN
    // no exceptions thrown

  }
Assembles the basic default fixture of the test:
The blueprint has 2 hostgroups, both of them contains the KERBEROS service (or KERBEROS_CLIENT)
The changing items are the configurations, that my come from the topology (bp + cct) or the hostg roups
ambari-server/src/test/java/org/apache/ambari/server/topology/validators/RequiredConfigPropertiesValidatorTest.java