Unit test improvements:

pkg/unittest/lib/unittest.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.
 
 /**
  * A library for writing dart unit tests.
  *
  * To import this library, use the pub package manager.
  * Create a pubspec.yaml file in your project and add
  * a dependency on unittest with the following lines:
@@ skipping 336 matching lines @@
     _callback = callback;
     _shouldCallBack = shouldCallBack;
     _isDone = isDone;
     _expectedCalls = expectedCalls;
     _testNum = _currentTest;
     _testCase = _tests[_currentTest];
     if (expectedCalls > 0) {
       _testCase.callbackFunctionsOutstanding++;
     }
     _id = '';
+    // If the callback is not an anonymous closure, try to get the
+    // name.
+    var fname = callback.toString();
+    var prefix = "Function '";
+    var pos = fname.indexOf(prefix);
+    if (pos > 0) {
+      pos += prefix.length;
+      var epos = fname.indexOf("'", pos);
+      if (epos > 0) {
+        _id = "${fname.substring(pos, epos)} ";
+      }
+    }
   }
 
   _SpreadArgsHelper(callback, shouldCallBack, isDone) {
     _init(callback, shouldCallBack, isDone);
   }
 
   _SpreadArgsHelper.fixedCallCount(callback, expectedCalls, id) {
     _init(callback, _checkCallCount, _allCallsDone, expectedCalls);
     if (id != null) {
       _id = "$id ";
@@ skipping 545 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 void TestFunction();