@Test
  public void testGetId() {
    Properties config = new Properties();
    config.setProperty(MCAST_PORT, "0");
    config.setProperty(LOCATORS, "");
    config.setProperty(NAME, "foobar");

    InternalDistributedSystem system = getSystem(config);
    try {

      DistributionManager dm = system.getDistributionManager();
      DistributedMember member = dm.getDistributionManagerId();

      assertEquals(member.getId(), system.getMemberId());
      assertTrue(member.getId().contains("foobar"));
    } finally {
      system.disconnect();
    }
  }
The method getId() returns a string that is used as a key identifier in the JMX and Admin APIs.
This test asserts that it matches the expected format. If you change DistributedMember.getId()
or DistributedSystem. getMemberId() you will need to look closely at the format, decide if it
is appropriate for JMX as the id for SystemMember mbeans and then adjust this test as needed.

Changing the id can result in bad keys in JMX and can result in numerous errors in Admin/JMX
tests.
geode-core/src/distributedTest/java/org/apache/geode/distributed/DistributedMemberDUnitTest.java