Changes to how we handle fancy stacks:

pkg/unittest/lib/src/config.dart

 // Copyright (c) 2011, 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 unittest;
 
 // A custom failure handler for [expect] that routes expect failures
 // to the config.
 class _ExpectFailureHandler extends DefaultFailureHandler {
   Configuration _config;
@@ skipping 37 matching lines @@
 
   /**
    * If true (the default), then tests will stop after the first failed
    * [expect]. If false, failed [expect]s will not cause the test
    * to stop (other exceptions will still terminate the test).
    */
   bool stopTestOnExpectFailure = true;
 
   // If stopTestOnExpectFailure is false, we need to capture failures, which
   // we do with this List.
-  final _testLogBuffer = <Pair<String, Trace>>[];
+  final _testLogBuffer = <Pair<String, String>>[];

[nweiz, 2013/08/15 23:03:25]

Trace implements StackTrace, so you can make this a Pair<String, StackTrace> and
avoid converting to a string until you actually need a string representation.

[gram, 2013/08/16 16:56:45]

Done.

[gram, 2013/08/16 16:56:45]

Done.

 
   /**
    * The constructor sets up a failure handler for [expect] that redirects
    * [expect] failures to [onExpectFailure].
    */
   Configuration() {
     configureExpectFailureHandler(new _ExpectFailureHandler(this));
   }
   /**
    * Called as soon as the unittest framework becomes initialized. This is done
    * even before tests are added to the test framework. It might be used to
    * determine/debug errors that occur before the test harness starts executing.
    * It is also used to tell the vm or browser that tests are going to be run
    * asynchronously and that the process should wait until they are done.
    */
   void onInit() {
+    formatStacks = false;
     _receivePort = new ReceivePort();
     _postMessage('unittest-suite-wait-for-done');
   }
 
   /** Called as soon as the unittest framework starts running. */
   void onStart() {}
 
   /**
    * Called when each test starts. Useful to show intermediate progress on
    * a test suite. Derived classes should call this first before their own
@@ skipping 62 matching lines @@
    * Handles failures from expect(). The default in
    * this base configuration is to throw an exception;
    */
   void onExpectFailure(String reason) {
     if (stopTestOnExpectFailure) {
       throw new TestFailure(reason);
     } else {
       try {
         throw '';
       } catch (_, stack) {
-        _testLogBuffer.add(
-            new Pair<String, Trace>(reason, new Trace.from(stack)));
+        var trace = _getTrace(stack);
+        if (trace == null) trace = stack;
+        _testLogBuffer.add(new Pair<String, String>(reason, trace.toString()));

[nweiz, 2013/08/15 23:03:25]

Why are you eagerly converting the stack trace to a string rather than just
making it a Pair<String, StackTrace>?

[gram, 2013/08/16 16:56:45]

Because I didn't realize Trace <- StackTrace. :-)

       }
     }
   }
   
   /**
    * Format a test result.
    */
   String formatResult(TestCase testCase) {
     var result = new StringBuffer();
     result.write(testCase.result.toUpperCase());
@@ skipping 65 matching lines @@
   // Currently e.message works in dartium, but not in dartc.
   void handleExternalError(e, String message, [stack]) =>
       _reportTestError('$message\nCaught $e', stack);
 
   _postMessage(String message) {
     // In dart2js browser tests, the JavaScript-based test controller
     // intercepts calls to print and listens for "secret" messages.
     print(message);
   }
 }