Improved error messages from unittest.

pkg/unittest/lib/src/description.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of matcher;
 
 /**
  * The default implementation of IDescription. This should rarely need
  * substitution, although conceivably it is a place where other languages
  * could be supported.
  */
 class StringDescription implements Description {
   var _out;
 
   /** Initialize the description with initial contents [init]. */
   StringDescription([String init = '']) {
     _out = init;
   }
 
+  int get length => _out.length;
+
   /** Get the description as a string. */
   String toString() => _out;
 
   /** Append some plain [text] to the description.  */
   Description add(String text) {
     _out = '${_out}${text}';
     return this;
   }
 
   /** Change the value of the description. */
@@ skipping 37 matching lines @@
     return this;
   }
 
   /** Escape the control characters in [string] so that they are visible. */
   _addEscapedString(String string) {
     add("'");
     add(escapeString(string));
     add("'");
   }
 }