The following can be observed in master branch:
The NPE comes from the following in TestEndToEndSplitTransaction :
Initial check of the code shows that TestEndToEndSplitTransaction uses TEST_UTIL instance which is created within TestEndToEndSplitTransaction. However, TestTableResource creates its own instance of HBaseTestingUtility.
Meaning TEST_UTIL.getMiniHBaseCluster() would return null, since the instance created by TestEndToEndSplitTransaction has hbaseCluster as null.