anchor.diff:      // to the next line.
       while (currentColumn != column) {
         if (currentColumn < NUM_COLUMNS - 1) {
  -        buffer.add(padRight('', columnWidths[currentColumn]));
  +        buffer.write(padRight('', columnWidths[currentColumn]));
         } else {
  -        buffer.add('\n');
  +        buffer.write('\n');
         }
         currentColumn = (currentColumn + 1) % NUM_COLUMNS;
       }
   
       if (column < columnWidths.length) {
         // Fixed-size column, so pad it.
  -      buffer.add(padRight(text, columnWidths[column]));
  +      buffer.write(padRight(text, columnWidths[column]));
       } else {
         // The last column, so just write it.
  -      buffer.add(text);
  +      buffer.write(text);
       }
   
       // Advance to the next column.
  
positive.code:   writeLine(int column, String text) {
      // Write any pending newlines.
      while (newlinesNeeded > 0) {
        buffer.add('\n');
        newlinesNeeded--;
      }
  
  
negative.code: /** Pads [source] to [length] by adding spaces at the end. */
  String padRight(String source, int length) {
    final result = new StringBuffer();
    result.write(source);
  
    while (result.length < length) {
      result.write(' ');
    }
  
    return result.toString();
  }
  