@Override
      public Object call() {
        TXManagerImpl mgr = getCache().getTxManager();
        assertThat(mgr.hostedTransactionsInProgressForTest()).isOne();
        mgr.memberDeparted(getCache().getDistributionManager(), member, true);
        assertThat(mgr.hostedTransactionsInProgressForTest()).isZero();
        return null;
      }
@return first key found on the given member
geode-core/src/distributedTest/java/org/apache/geode/internal/cache/RemoteTransactionDUnitTest.java