.when(mockFlushable)
          .flush();
    }
  }

  // Flush the flushable using the Flushables, passing in the swallowException
  // parameter. expectThrown determines whether we expect an exception to
  // be thrown by Flushables.flush;
  private void doFlush(Flushable flushable, boolean swallowException, boolean expectThrown)
      throws IOException {
    try {
      Flushables.flush(flushable, swallowException);

   *     method
   * @throws IOException if {@code swallowIOException} is false and {@link Flushable#flush} throws
   *     an {@code IOException}.
   * @see Closeables#close
   */
  public static void flush(Flushable flushable, boolean swallowIOException) throws IOException {
    try {
      flushable.flush();
    } catch (IOException e) {
      if (swallowIOException) {

    super.write(c);
    flush(); // flush write to TestOutputStream to get its behavior
  }

  @Override
  public void write(char[] cbuf, int off, int len) throws IOException {
    super.write(cbuf, off, len);
    flush();
  }

  @Override
  public void write(String str, int off, int len) throws IOException {
    super.write(str, off, len);
    flush();
  }

  public boolean closed() {

  public Writer openStream() throws IOException {
    // using TestByteSink's output stream to get option behavior, so flush to it on every write
    return new FilterWriter(new OutputStreamWriter(byteSink.openStream(), UTF_8)) {
      @Override
      public void write(int c) throws IOException {
        super.write(c);
        flush();
      }

      @Override
      public void write(char[] cbuf, int off, int len) throws IOException {

        // == true. Then there is a final call to flush.
        CoderResult result;
        if (doneFlushing) {
          result = CoderResult.UNDERFLOW;
        } else if (doneEncoding) {
          result = encoder.flush(byteBuffer);
        } else {
          result = encoder.encode(charBuffer, byteBuffer, endOfInput);
        }

      return this;
    }

    @Override
    public Appendable append(CharSequence csq, int start, int end) {
      result.append(csq, start, end);
      return this;
    }

    @Override
    public void flush() {
      flushed = true;
    }

    @Override
    public void close() {
      closed = true;
    }
  }

  public void testWriteMethods() throws IOException {

    checkNotClosed();
    // tricky: append takes start, end pair...
    target.append(str, off, off + len);
  }

  @Override
  public void flush() throws IOException {
    checkNotClosed();
    if (target instanceof Flushable) {
      ((Flushable) target).flush();
    }
  }

  @Override
  public void close() throws IOException {
    this.closed = true;
    if (target instanceof Closeable) {

      return this;
    }

    @Override
    public Appendable append(CharSequence csq, int start, int end) {
      result.append(csq, start, end);
      return this;
    }

    @Override
    public void flush() {
      flushed = true;
    }

    @Override
    public void close() {
      closed = true;
    }
  }

  public void testWriteMethods() throws IOException {

    super.write(c);
    flush(); // flush write to TestOutputStream to get its behavior
  }

  @Override
  public void write(char[] cbuf, int off, int len) throws IOException {
    super.write(cbuf, off, len);
    flush();
  }

  @Override
  public void write(String str, int off, int len) throws IOException {
    super.write(str, off, len);
    flush();
  }

  public boolean closed() {

    out.write(b, off, len);
  }

  @Override
  public synchronized void close() throws IOException {
    out.close();
  }

  @Override
  public synchronized void flush() throws IOException {
    out.flush();
  }

  /**
   * Checks if writing {@code len} bytes would go over threshold, and switches to file buffering if
   * so.
   */
  @GuardedBy("this")