StringBuilder builder = new StringBuilder();
    Writer writer = new AppendableWriter(builder);

    writer.write("Hello".toCharArray());
    writer.write(',');
    writer.write(0xBEEF0020); // only lower 16 bits are important
    writer.write("Wo");
    writer.write("Whirled".toCharArray(), 3, 2);
    writer.write("Mad! Mad, I say", 2, 2);

    assertEquals("Hello, World!", builder.toString());
  }

    if (JAVA_IO_TMPDIR.value().equals("/sdcard")) {
      assertThrows(IOException.class, () -> out.write(data));
      return;
    }
    out.write(data);
    assertTrue(Arrays.equals(data, source.read()));

    out.close();
    assertThrows(IOException.class, () -> out.write(42));

    // Verify that write had no effect
    assertTrue(Arrays.equals(data, source.read()));
    out.reset();
  }

    Writer writer = sink.openStream();
    try {
      writer.write(data);
    } finally {
      writer.close();
    }

    assertContainsExpectedString();
  }

  public void testOpenBufferedStream() throws IOException {
    Writer writer = sink.openBufferedStream();
    try {
      writer.write(data);
    } finally {
      writer.close();
    }

    assertFalse(source.wasStreamClosed());

    StringWriter writer = new StringWriter();
    char[] buf = new char[64];
    int read;
    while ((read = reader.read(buf)) != -1) {
      writer.write(buf, 0, read);
    }
    reader.close();
    writer.close();

    assertTrue(source.wasStreamClosed());
    assertEquals(STRING, writer.toString());
  }

  public void testCopyTo_appendable() throws IOException {

  public boolean closed() {
    return closed;
  }

  @Override
  public void write(byte[] b, int off, int len) throws IOException {
    throwIf(closed);
    throwIf(WRITE_THROWS);
    super.write(b, off, len);
  }

  @Override
  public void write(int b) throws IOException {
    throwIf(closed);
    throwIf(WRITE_THROWS);
    super.write(b);
  }

  @Override
  public void close() throws IOException {

  public void setUp() {
    sink = new TestCharSink();
  }

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

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

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

    assertEquals(written, counter.getCount());

    counter.write(0);
    written += 1;
    assertEquals(written, out.size());
    assertEquals(written, counter.getCount());

    byte[] data = new byte[10];
    counter.write(data);
    written += 10;
    assertEquals(written, out.size());
    assertEquals(written, counter.getCount());

    counter.write(data, 0, 5);
    written += 5;
    assertEquals(written, out.size());

    assertEquals(written, counter.getCount());

    counter.write(0);
    written += 1;
    assertEquals(written, out.size());
    assertEquals(written, counter.getCount());

    byte[] data = new byte[10];
    counter.write(data);
    written += 10;
    assertEquals(written, out.size());
    assertEquals(written, counter.getCount());

    counter.write(data, 0, 5);
    written += 5;
    assertEquals(written, out.size());

    public CharSink createSink() throws IOException {
      File file = createFile();
      if (initialString != null) {
        Writer writer = new OutputStreamWriter(new FileOutputStream(file), Charsets.UTF_8);
        try {
          writer.write(initialString);
        } finally {
          writer.close();
        }
        return Files.asCharSink(file, Charsets.UTF_8, FileWriteMode.APPEND);
      }

  /** Returns the number of bytes written. */
  public long getCount() {
    return count;
  }

  @Override
  public void write(byte[] b, int off, int len) throws IOException {
    out.write(b, off, len);
    count += len;
  }

  @Override
  public void write(int b) throws IOException {
    out.write(b);
    count++;
  }

  // Overriding close() because FilterOutputStream's close() method pre-JDK8 has bad behavior: