@Test
  public void testClientToClientDeltaPropagation() throws Exception {
    initialise(false);
    // set expected value on s1,s1 and c2
    server.invoke(() -> ClientToServerDeltaDUnitTest.setFirstSecondUpdate(putDelta[0],
        putDelta[2]));
    server2.invoke(() -> ClientToServerDeltaDUnitTest.setFirstSecondUpdate(putDelta[0],
        putDelta[2]));
    client2.invoke(() -> ClientToServerDeltaDUnitTest.setFirstSecondUpdate(putDelta[0],
        putDelta[2]));

    client.invoke(() -> ClientToServerDeltaDUnitTest.putDelta(KEY1));

    Thread.sleep(5000);

    assertTrue("To Delta Propagation feature NOT used.",
        client.invoke(DeltaTestImpl::toDeltaFeatureUsed));
    assertTrue("From Delta Propagation feature NOT used.",
        server.invoke(DeltaTestImpl::fromDeltaFeatureUsed));
    // toDelta() should not be invoked
    assertFalse("To Delta Propagation feature used.",
        server.invoke(DeltaTestImpl::toDeltaFeatureUsed));
    assertTrue("From Delta Propagation feature NOT used.",
        server2.invoke(DeltaTestImpl::fromDeltaFeatureUsed));
    // toDelta() should not be invoked
    assertFalse("To Delta Propagation feature used.",
        server2.invoke(DeltaTestImpl::toDeltaFeatureUsed));
    assertTrue("from Delta Propagation feature NOT used.",
        client2.invoke(DeltaTestImpl::fromDeltaFeatureUsed));

    boolean err =
        server.invoke(ClientToServerDeltaDUnitTest::getError);
    err = server2.invoke(ClientToServerDeltaDUnitTest::getError);
    err = client2.invoke(ClientToServerDeltaDUnitTest::getError);
    assertFalse("validation fails", err);
  }
This test does the following for single key (<b> full cycle</b>):<br>
1)Verifies that client-server, peer-peer and server-client processing delta<br>
geode-cq/src/distributedTest/java/org/apache/geode/internal/cache/tier/sockets/ClientToServerDeltaDUnitTest.java