* {@link ByteSource} returned by {@link #asByteSource} is garbage collected.
   *
   * @param fileThreshold the number of bytes before the stream should switch to buffering to a file
   * @throws IllegalArgumentException if {@code fileThreshold} is negative
   */
  public FileBackedOutputStream(int fileThreshold) {
    this(fileThreshold, false);
  }

  /**

  }

  private void testThreshold(
      int fileThreshold, int dataSize, boolean singleByte, boolean resetWhenGarbageCollected)
      throws IOException {
    byte[] data = newPreFilledByteArray(dataSize);
    FileBackedOutputStream out =
        new FileBackedOutputStream(fileThreshold, resetWhenGarbageCollected);
    ByteSource source = out.asByteSource();
    int chunk1 = min(dataSize, fileThreshold);
    int chunk2 = dataSize - chunk1;