Improved error messages from unittest.

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 100 matching lines @@
   }
 
   Description describe(Description description) {
     if (_valueInDescription) {
       return description.add(_comparisonDescription).add(' ').
           addDescriptionOf(_value);
     } else {
       return description.add(_comparisonDescription);
     }
   }
+
+  Description describeMismatch(item, Description mismatchDescription,
+                               MatchState matchState, bool verbose) {
+    mismatchDescription.add('is not ');
+    return describe(mismatchDescription);
+  }
 }
 
 /**
  * Returns a matcher which matches if the match argument is within [delta]
  * of some [value]; i.e. if the match argument is greater than
  * than or equal [value]-[delta] and less than or equal to [value]+[delta].
  */
 Matcher closeTo(value, delta) => new _IsCloseTo(value, delta);
 
 class _IsCloseTo extends BaseMatcher {
@@ skipping 17 matching lines @@
         addDescriptionOf(_value);
 
   Description describeMismatch(item, Description mismatchDescription,
                                MatchState matchState, bool verbose) {
     if (item is !num) {
       return mismatchDescription.add(' not numeric');
     } else {
       var diff = item - _value;
       if (diff < 0) diff = -diff;
       return mismatchDescription.
-          add(' differed by ').
+          add(' differs 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].
  */
 Matcher inInclusiveRange(low, high) => new _InRange(low, high, true, true);
@@ skipping 50 matching lines @@
       return mismatchDescription.
           addDescriptionOf(item).
           add(' not numeric');
     } else {
       return super.describeMismatch(item, mismatchDescription,
           matchState, verbose);
     }
   }
 }