@BeforeClass
  public static void beforeClass() throws Exception {
    Properties props = new Properties();
    props.setProperty(MCAST_PORT, "0");
    ds = DistributedSystem.connect(props);
    tm = TransactionManagerImpl.getTransactionManager();
  }
Test TransactionManagerImpl methods not tested by UserTransactionImplTest
geode-core/src/integrationTest/java/org/apache/geode/internal/jta/TransactionManagerImplJUnitTest.java