@Override
  public final void preTearDownCacheTestCase() throws Exception {
    Invoke.invokeInEveryVM(new SerializableCallable() {

      @Override
      public Object call() throws Exception {
        puttingThread = null;
        return null;
      }
    });
  }
Tests interrupting gemfire threads and seeing what happens
geode-core/src/distributedTest/java/org/apache/geode/internal/cache/InterruptClientServerDUnitTest.java