Improved error messages from unittest.

pkg/unittest/lib/src/string_matchers.dart

Index: pkg/unittest/lib/src/string_matchers.dart
===================================================================
--- pkg/unittest/lib/src/string_matchers.dart	(revision 24002)
+++ pkg/unittest/lib/src/string_matchers.dart	(working copy)
@@ -18,7 +18,7 @@
     _matchValue = _value.toLowerCase();
   }
 
-  bool matches(item, MatchState mismatchState) =>
+  bool matches(item, Map matchState) =>
       item is String && _matchValue == item.toLowerCase();
 
   Description describe(Description description) =>
@@ -44,17 +44,18 @@
     _matchValue = collapseWhitespace(_value);
   }
 
-  bool matches(item, MatchState matchState) =>
+  bool matches(item, Map matchState) =>
       item is String && _matchValue == collapseWhitespace(item);
 
   Description describe(Description description) =>
     description.addDescriptionOf(_matchValue).add(' ignoring whitespace');
 
   Description describeMismatch(item, Description mismatchDescription,
-                               MatchState matchState, bool verbose) {
+                               Map matchState, bool verbose) {
     if (item is String) {
-      return mismatchDescription.add('was ').
-          addDescriptionOf(collapseWhitespace(item));
+      return mismatchDescription.add('is ').
+          addDescriptionOf(collapseWhitespace(item)).
+          add(' with whitespace compressed');
     } else {
       return super.describeMismatch(item, mismatchDescription,
           matchState, verbose);
@@ -96,7 +97,7 @@
 
   const _StringStartsWith(this._prefix);
 
-  bool matches(item, MatchState matchState) =>
+  bool matches(item, Map matchState) =>
       item is String && item.startsWith(_prefix);
 
   Description describe(Description description) =>
@@ -115,7 +116,7 @@
 
   const _StringEndsWith(this._suffix);
 
-  bool matches(item, MatchState matchState) =>
+  bool matches(item, Map matchState) =>
       item is String && item.endsWith(_suffix);
 
   Description describe(Description description) =>
@@ -139,7 +140,7 @@
 
   const _StringContainsInOrder(this._substrings);
 
-  bool matches(item, MatchState matchState) {
+  bool matches(item, Map matchState) {
     if (!(item is String)) {
       return false;
     }
@@ -178,7 +179,7 @@
     }
   }
 
-  bool matches(item, MatchState matchState) =>
+  bool matches(item, Map matchState) =>
     item is String ? _regexp.hasMatch(item) : false;
 
   Description describe(Description description) =>
@@ -190,7 +191,7 @@
 abstract class _StringMatcher extends BaseMatcher {
   const _StringMatcher();
   Description describeMismatch(item, Description mismatchDescription,
-                               MatchState matchState, bool verbose) {
+                               Map matchState, bool verbose) {
     if (!(item is String)) {
       return mismatchDescription.
           addDescriptionOf(item).