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

pkg/unittest/lib/src/operator_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;
 
 /**
  * This returns a matcher that inverts [matcher] to its logical negation.
  */
 Matcher isNot(matcher) => new _IsNot(wrapMatcher(matcher));
@@ skipping 76 matching lines @@
          };
          return false;
        }
      }
      return true;
   }
 
   Description describeMismatch(item, Description mismatchDescription,
                                MatchState matchState, bool verbose) {
     var matcher = matchState.state['matcher'];
-    mismatchDescription.addDescriptionOf(matcher).add(' ');
-        matcher.describeMismatch(item, mismatchDescription,
-            matchState.state['state'], verbose);
+    matcher.describeMismatch(item, mismatchDescription,
+        matchState.state['state'], verbose);
+    mismatchDescription.add(" (wasn't ").addDescriptionOf(matcher).add(')');
     return mismatchDescription;
   }
 
   Description describe(Description description) =>
       description.addAll('(', ' and ', ')', _matchers);
 }
 
 /**
  * Matches if any of the given matchers evaluate to true. The
  * arguments can be a set of matchers as separate parameters
@@ skipping 62 matching lines @@
          return true;
        }
      }
      return false;
   }
 
   Description describe(Description description) =>
     description.addAll('(', ' or ', ')', _matchers);
 }