@Override
          public Integer call() {
            // lock, inc count, and unlock until stop_testFairness is set true
            final AtomicInteger lockCount = new AtomicInteger(0);
            try {
              DistributedLockService service =
                  DistributedLockService.getServiceNamed(serviceName);
              while (!stop_testFairness) {
                assertThat(service.lock(lock, -1, -1)).isTrue();
                lockCount.incrementAndGet();
                service.unlock(lock);
              }
            } catch (VirtualMachineError e) {
              SystemFailure.initiateFailure(e);
              throw e;
            } catch (Throwable t) {
              logger.warn(t);
              fail(t.getMessage());
            } finally {
              return lockCount.get();
            }
          }
Connects a DistributedSystem, saves it in static variable "system"
geode-core/src/distributedTest/java/org/apache/geode/distributed/DistributedLockServiceDUnitTest.java