private static void verifyDataSerializerIDMap(int expected) {
    int actual = InternalDataSerializer.getIdsToHoldersMap().size();
    assertEquals(expected, actual);
  }
Register two DataSerializers on the server and verify that they get propagated to client.
geode-core/src/distributedTest/java/org/apache/geode/internal/cache/tier/sockets/DataSerializerPropagationDUnitTest.java