@Override
    public CharSource createSource(String string) throws IOException {
      checkNotNull(string);
      Path file = createFile();
      try (Writer writer = java.nio.file.Files.newBufferedWriter(file, Charsets.UTF_8)) {
        writer.write(string);
      }
      return MoreFiles.asCharSource(file, Charsets.UTF_8);
    }

    @Override
    public String getExpected(String string) {

  }

  /**
   * Returns a buffered writer that writes to a file using the given character set.
   *
   * <p><b>{@link java.nio.file.Path} equivalent:</b> {@link
   * java.nio.file.Files#newBufferedWriter(java.nio.file.Path, Charset,
   * java.nio.file.OpenOption...)}.
   *
   * @param file the file to write to
   * @param charset the charset used to encode the output stream; see {@link StandardCharsets} for