@Test
  public void registerClientExistingClientDoesNotUpdateTimeOrIncrementStat()
      throws InterruptedException {
    ClientProxyMembershipID mockId = mock(ClientProxyMembershipID.class);
    clientHealthMonitor.registerClient(mockId);
    Long expectedTime = clientHealthMonitor.getClientHeartbeats().get(mockId);

    Thread.sleep(2);
    clientHealthMonitor.registerClient(mockId);
    assertThat(clientHealthMonitor.getClientHeartbeats().get(mockId)).isNotNull()
        .isEqualTo(expectedTime);

    // incremented 1 time for the initial registerClient.
    verify(mockStats).incClientRegisterRequests();
  }
This is a functional-test for <code>ClientHealthMonitor</code>.
geode-core/src/test/java/org/apache/geode/internal/cache/tier/sockets/ClientHealthMonitorTest.java