public void testOpenBufferedStream() throws IOException {
    OutputStream out = sink.openBufferedStream();
    assertTrue(sink.wasStreamOpened());
    assertFalse(sink.wasStreamClosed());

    out.write(new byte[] {1, 2, 3, 4});
    out.close();

    assertTrue(sink.wasStreamClosed());
    assertArrayEquals(new byte[] {1, 2, 3, 4}, sink.getBytes());
  }

  public void testWrite_bytes() throws IOException {

  public void testOpenBufferedStream() throws IOException {
    OutputStream out = sink.openBufferedStream();
    assertTrue(sink.wasStreamOpened());
    assertFalse(sink.wasStreamClosed());

    out.write(new byte[] {1, 2, 3, 4});
    out.close();

    assertTrue(sink.wasStreamClosed());
    assertArrayEquals(new byte[] {1, 2, 3, 4}, sink.getBytes());
  }

  public void testWrite_bytes() throws IOException {

    assertFalse(sink.wasStreamClosed());

    writer.write(STRING);
    writer.close();

    assertTrue(sink.wasStreamClosed());
    assertEquals(STRING, sink.getString());
  }

  public void testWrite_string() throws IOException {
    assertEquals("", sink.getString());
    sink.write(STRING);

    assertTrue(sink.wasStreamOpened() && sink.wasStreamClosed());
    assertEquals(STRING, sink.getString());

    return new String(byteSink.getBytes(), UTF_8);
  }

  @Override
  public boolean wasStreamOpened() {
    return byteSink.wasStreamOpened();
  }

  @Override
  public boolean wasStreamClosed() {
    return byteSink.wasStreamClosed();
  }

  @Override
  public Writer openStream() throws IOException {
    // using TestByteSink's output stream to get option behavior, so flush to it on every write

    assertFalse(sink.wasStreamClosed());

    writer.write(STRING);
    writer.close();

    assertTrue(sink.wasStreamClosed());
    assertEquals(STRING, sink.getString());
  }

  public void testWrite_string() throws IOException {
    assertEquals("", sink.getString());
    sink.write(STRING);

    assertTrue(sink.wasStreamOpened() && sink.wasStreamClosed());
    assertEquals(STRING, sink.getString());

  }

  @Override
  public boolean wasStreamOpened() {
    return byteSource.wasStreamOpened();
  }

  @Override
  public boolean wasStreamClosed() {
    return byteSource.wasStreamClosed();
  }

  @Override
  public Reader openStream() throws IOException {
    return new InputStreamReader(byteSource.openStream(), UTF_8);
  }

  }

  byte[] getBytes() {
    return bytes.toByteArray();
  }

  @Override
  public boolean wasStreamOpened() {
    return outputStreamOpened;
  }

  @Override
  public boolean wasStreamClosed() {
    return outputStreamClosed;
  }

  @Override
  public OutputStream openStream() throws IOException {
    outputStreamOpened = true;
    bytes.reset(); // truncate
    return new Out();
  }

  }

  @Override
  public boolean wasStreamOpened() {
    return byteSource.wasStreamOpened();
  }

  @Override
  public boolean wasStreamClosed() {
    return byteSource.wasStreamClosed();
  }

  @Override
  public Reader openStream() throws IOException {
    return new InputStreamReader(byteSource.openStream(), UTF_8);
  }

    return new String(byteSink.getBytes(), UTF_8);
  }

  @Override
  public boolean wasStreamOpened() {
    return byteSink.wasStreamOpened();
  }

  @Override
  public boolean wasStreamClosed() {
    return byteSink.wasStreamClosed();
  }

  @Override
  public Writer openStream() throws IOException {
    // using TestByteSink's output stream to get option behavior, so flush to it on every write

 */
public interface TestStreamSupplier {

  /** Returns whether or not a new stream was opened. */
  boolean wasStreamOpened();

  /** Returns whether or not an open stream was closed. */
  boolean wasStreamClosed();