@Test
  public void testIsDistributedDoesNotThrowNPE() {
    TXManagerImpl txMgr = (TXManagerImpl) cache.getCacheTransactionManager();
    cache.getDistributedSystem().disconnect();
    callIsDistributed(txMgr);
  }
test that timeout of Long.MAX_VALUE does not return immediately
geode-core/src/integrationTest/java/org/apache/geode/internal/cache/TXManagerImplJUnitTest.java