Added test setup/teardown.

lib/unittest/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.
 /**
  * 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 = '';
+  var _out;
+
+  /**
+   * Initialize the description with initial contents [init].
+   */
+  StringDescription([String init = '']) {
+    _out = init;
+  }
 
   /**
    * Get the description as a string.
    */
   String toString() => _out;
 
   /**
    * Append some plain [text] to the description.
    */
   Description add(String text) {
@@ skipping 61 matching lines @@
     else if (ch == '\n')
       return '\\n';
     else if (ch == '\r')
       return '\\r';
     else if (ch == '\t')
       return '\\t';
     else
       return ch;
   }
 }