public void pauseFlusherForTesting() {
    assert fp == null;
    fp = new FlushPauser();
    try {
      addAsyncItem(fp, true);
    } catch (InterruptedException ex) {
      Thread.currentThread().interrupt();
      throw new IllegalStateException("unexpected interrupt in test code", ex);
    }
  }
After tests call this method they must call flushForTesting.
geode-core/src/main/java/org/apache/geode/internal/cache/DiskStoreImpl.java