@Test
  public void testForCA() throws Exception {
    callbackArg = "cbArg";
    getOtherVm().invoke(new SerializableCallable() {
      @Override
      public Object call() throws Exception {
        callbackArg = "cbArg";
        return null;
      }
    });
    doTest();
  }
make sure callback arg is NOT_AVAILABLE in all the places it should be
geode-core/src/distributedTest/java/org/apache/geode/cache30/CallbackArgDUnitTest.java