@Before
  public void setup() {
    // stress testing needs this so that join attempts don't give up too soon
    Invoke.invokeInEveryVM(() -> System.setProperty("p2p.joinTimeout", "120000"));
    VM locatorVM = VM.getVM(4);
    final int port = locatorVM.invoke(() -> {
      System.setProperty(BYPASS_DISCOVERY_PROPERTY, "true");
      // set a big weight on the locator to prevent total shutdown when one server decides
      // to kill the other server
      System.setProperty(GeodeGlossary.GEMFIRE_PREFIX + "member-weight", "100");
      return Locator.startLocatorAndDS(0, new File(""), new Properties()).getPort();
    });
    Invoke.invokeInEveryVM(() -> locatorPort = port);
    locatorPort = port;
  }
tests for the concurrentMapOperations. there are more tests in ClientServerMiscDUnitTest
geode-core/src/distributedTest/java/org/apache/geode/internal/cache/ConcurrentMapOpsDUnitTest.java