Add pretty-printing to unittest and more thoroughly print values.

pkg/unittest/lib/src/numeric_matchers.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;
 
 /**
  * Returns a matcher which matches if the match argument is greater
  * than the given [value].
  */
@@ skipping 132 matching lines @@
 
   Description describe(Description description) =>
     description.add('a numeric value within ').
         addDescriptionOf(_delta).
         add(' of ').
         addDescriptionOf(_value);
 
   Description describeMismatch(item, Description mismatchDescription,
                                MatchState matchState, bool verbose) {
     if (item is !num) {
-      return mismatchDescription.
-          addDescriptionOf(item).
-          add(' not numeric');
+      return mismatchDescription.add(' not numeric');
     } else {
       var diff = item - _value;
       if (diff < 0) diff = -diff;
       return mismatchDescription.
-          addDescriptionOf(item).
           add(' differed by ').
           addDescriptionOf(diff);
     }
   }
 }
 
 /**
  * Returns a matcher which matches if the match argument is greater
  * than or equal to [low] and less than or equal to [high].
  */
@@ skipping 51 matching lines @@
       return mismatchDescription.
           addDescriptionOf(item).
           add(' not numeric');
     } else {
       return super.describeMismatch(item, mismatchDescription,
           matchState, verbose);
     }
   }
 }