Improved error messages from unittest.

pkg/unittest/lib/unittest.dart

 // Copyright (c) 2013, 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.
 
 /**
  * A library for writing dart unit tests.
  *
  * ## Installing ##
  *
  * Use [pub][] to install this package. Add the following to your `pubspec.yaml`
@@ skipping 845 matching lines @@
 
 /** Enable a test by ID. */
 void enableTest(int testId) => _setTestEnabledState(testId, true);
 
 /** Disable a test by ID. */
 void disableTest(int testId) => _setTestEnabledState(testId, false);
 
 /** Signature for a test function. */
 typedef dynamic TestFunction();
 
+/**
+ * A flag that controls whether we hide unittest details in exception stacks.
+ * Useful to disable when debugging unittest or matcher customizations.
+ */
+bool formatStacks = true;
+
 // Stack formatting utility. Strips extraneous content from a stack trace.
 // Stack frame lines are parsed with a regexp, which has been tested
 // in Chrome, Firefox and the VM. If a line fails to be parsed it is
 // included in the output to be conservative.
 //
 // The output stack consists of everything after the call to TestCase._run.
 // If we see an 'expect' in the frame we will prune everything above that
 // as well.
 final _frameRegExp = new RegExp(
     r'^\s*' // Skip leading spaces.
     r'(?:'  // Group of choices for the prefix.
       r'(?:#\d+\s*)|' // Skip VM's #<frameNumber>.
       r'(?:at )|'     // Skip Firefox's 'at '.
       r'(?:))'        // Other environments have nothing here.
     r'(.+)'           // Extract the function/method.
     r'\s*[@\(]'       // Skip space and @ or (.
     r'('              // This group of choices is for the source file.
       r'(?:.+:\/\/.+\/[^:]*)|' // Handle file:// or http:// URLs.
       r'(?:dart:[^:]*)|'  // Handle dart:<lib>.
       r'(?:package:[^:]*)' // Handle package:<path>
     r'):([:\d]+)[\)]?$'); // Get the line number and optional column number.
 
 String _formatStack(stack) {
+  if (!formatStacks) {

[Siggi Cherem (dart-lang), 2013/06/14 01:20:56]

nit: use fast-exit pattern 
if (!formatStacks) return "$stack";

+    return "$stack";
+  }
   var lines;
   if (stack is StackTrace) {
     lines = stack.toString().split('\n');
   } else if (stack is String) {
     lines = stack.split('\n');
   } else {
     return stack.toString();
   }
 
   // Calculate the max width of first column so we can
@@ skipping 33 matching lines @@
         }
         sb.write(location);
         sb.write(' ');
         sb.write(position);
         sb.write('\n');
       }
     }
   }
   return sb.toString();
 }