@Override
        public void beforeCreate2(EntryEvent event) throws CacheWriterException {
          Integer key = (Integer) event.getKey();
          if (key % 2 == 0) {
            Object callbackArgument = event.getCallbackArgument();
            assertThat(createCallbackArg).isEqualTo(callbackArgument);
          } else {
            Object callbackArgument = event.getCallbackArgument();
            assertThat(callbackArgument).isNull();
          }
        }
Tests that consecutive puts have the callback assigned appropriately.
geode-core/src/distributedTest/java/org/apache/geode/cache/ConnectionPoolDUnitTest.java