ByteStreams.readFully(newTestStream(10), b, 0, 10);
    assertThat(b).isEqualTo(newPreFilledByteArray(10));

    Arrays.fill(b, (byte) 0);
    ByteStreams.readFully(newTestStream(10), b, 0, 5);
    assertThat(b).isEqualTo(new byte[] {0, 1, 2, 3, 4, 0, 0, 0, 0, 0});
  }

  public void testSkipFully() throws IOException {
    byte[] bytes = newPreFilledByteArray(100);
    skipHelper(0, 0, new ByteArrayInputStream(bytes));

    ByteStreams.readFully(newTestStream(10), b, 0, 10);
    assertThat(b).isEqualTo(newPreFilledByteArray(10));

    Arrays.fill(b, (byte) 0);
    ByteStreams.readFully(newTestStream(10), b, 0, 5);
    assertThat(b).isEqualTo(new byte[] {0, 1, 2, 3, 4, 0, 0, 0, 0, 0});
  }

  public void testSkipFully() throws IOException {
    byte[] bytes = newPreFilledByteArray(100);
    skipHelper(0, 0, new ByteArrayInputStream(bytes));

    FileBackedOutputStream out = new FileBackedOutputStream(/* fileThreshold= */ 10);
    ByteSource source = out.asByteSource();

    byte[] chunk1 = newPreFilledByteArray(8); // Below threshold
    byte[] chunk2 = newPreFilledByteArray(5); // Crosses threshold
    byte[] chunk3 = newPreFilledByteArray(20); // More data to file

    out.write(chunk1);
    assertThat(out.getFile()).isNull();

    out.write(chunk2);

    // Source of length 5
    AppendableByteSource source = new AppendableByteSource(newPreFilledByteArray(5));

    // Slice it starting at offset 10.
    ByteSource slice = source.slice(10, 5);

    // Open a stream to the slice.
    InputStream in = slice.openStream();

    // Append 10 more bytes to the source.
    source.append(newPreFilledByteArray(5, 10));

    // Source of length 5
    AppendableByteSource source = new AppendableByteSource(newPreFilledByteArray(5));

    // Slice it starting at offset 10.
    ByteSource slice = source.slice(10, 5);

    // Open a stream to the slice.
    InputStream in = slice.openStream();

    // Append 10 more bytes to the source.
    source.append(newPreFilledByteArray(5, 10));

    assertThat(Files.toString(temp, UTF_16LE)).isEqualTo(I18N);
  }

  public void testWriteBytes() throws IOException {
    File temp = createTempFile();
    byte[] data = newPreFilledByteArray(2000);
    Files.write(data, temp);
    assertThat(Files.toByteArray(temp)).isEqualTo(data);

    assertThrows(NullPointerException.class, () -> Files.write(null, temp));
  }