}
    } else {
      out.write(b, off, len);
    }
    out.flush(); // for coverage
  }

  // TODO(chrisn): only works if we ensure we have crossed file threshold

  public void testWriteErrorAfterClose() throws Exception {
    byte[] data = newPreFilledByteArray(100);
    FileBackedOutputStream out = new FileBackedOutputStream(50);
    ByteSource source = out.asByteSource();