Unit test improvements:

pkg/unittest/lib/src/expect.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;
 
 /**
  * Some matchers, like those for Futures and exception testing,
  * can fail in asynchronous sections, and throw exceptions.
  * A user of this library will typically want to catch and handle 
@@ skipping 104 matching lines @@
 ErrorFormatter _assertErrorFormatter = null;
 
 // The default error formatter implementation.
 String _defaultErrorFormatter(actual, Matcher matcher, String reason,
     MatchState matchState, bool verbose) {
   var description = new StringDescription();
   description.add('Expected: ').addDescriptionOf(matcher).
       add('\n     but: ');
   matcher.describeMismatch(actual, description, matchState, verbose);
   description.add('.\n');
-  if (verbose && actual is Iterable) {
-    description.add('Actual: ').addDescriptionOf(actual).add('\n');
+  if (verbose) {
+    if (actual is Iterable) {
+      description.add('Actual: ').addDescriptionOf(actual).add('\n');
+    } else if (actual is Map) {
+      description.add('Actual: ');
+      var count = 25;

[Siggi Cherem (dart-lang), 2013/02/12 21:06:15]

seems quite arbitrary to use 25 =)... maybe 10? (especially since there is 1 per
line?)

[gram, 2013/02/12 21:08:09]

As you say, it is arbitrary. 10 feels too small for me though.

+      for (var k in actual.keys) {

[Siggi Cherem (dart-lang), 2013/02/12 21:06:15]

Is this description used for any other purpose? Will it matter that keys are not
guaranteed to any particular order?

[gram, 2013/02/12 21:08:09]

No. Unlike the matcher description; this is the error description.

+        if (count == 0) {
+          description.add('...\n');
+          break;
+        }
+        description.addDescriptionOf(k);
+        description.add(' : ');
+        description.addDescriptionOf(actual[k]);
+        description.add('\n');
+        --count;
+      }
+    }
   }
   if (reason != null) {
     description.add(reason).add('\n');
   }
   return description.toString();
 }
 
 /**
  * Changes or resets to default the failure message formatter for expect().
  * [formatter] is a reference to the new formatter; if this is omitted or
  * null then the failure formatter is reset to the default. The new
  * formatter is returned; this allows custom expect handlers to easily
  * get a reference to the default formatter.
  */
 ErrorFormatter configureExpectFormatter([ErrorFormatter formatter = null]) {
   if (formatter == null) {
     formatter = _defaultErrorFormatter;
   }
   return _assertErrorFormatter = formatter;
 }