Improved error messages from unittest.

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;
 
 /** The objects thrown by the default failure handler. */
 class TestFailure {
   String _message;
 
@@ skipping 123 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');
 
   var mismatchDescription = new StringDescription();
   matcher.describeMismatch(actual, mismatchDescription, matchState, verbose);
-  description.add('     But: ')
-      .add(mismatchDescription.toString()).add('.\n');
 
-  description.add('Actual: ').addDescriptionOf(actual);
+  description.add('  Actual: ').addDescriptionOf(actual);
+  var info = mismatchDescription.toString();
+  if (info.length > 0) {

[Siggi Cherem (dart-lang), 2013/06/12 00:34:45]

how about use mismatchDescription.length here?

[gram, 2013/06/13 19:06:15]

Done.

+    description.add('   Which: ${info}\n');

[Siggi Cherem (dart-lang), 2013/06/12 00:34:45]

then this can simply be $mispatchDescription

[Siggi Cherem (dart-lang), 2013/06/12 00:34:45]

"   Which:" => " Reason:" ?

[gram, 2013/06/13 19:06:15]

Done.

[gram, 2013/06/13 19:06:15]

"Which" scans better IMO.

+  }
   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;
 }