* @param input the size of the input source
   * @param offset the first argument to {@link ByteSource#slice}
   * @param length the second argument to {@link ByteSource#slice}
   * @param expectRead the number of bytes we expect to read
   */
  private static void assertCorrectSlice(int input, int offset, long length, int expectRead)
      throws IOException {

   * @param input the size of the input source
   * @param offset the first argument to {@link ByteSource#slice}
   * @param length the second argument to {@link ByteSource#slice}
   * @param expectRead the number of bytes we expect to read
   */
  private static void assertCorrectSlice(int input, int offset, long length, int expectRead)
      throws IOException {