Make the scheduled_test schedule keep track of multiple errors.

pkg/scheduled_test/lib/scheduled_test.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.
 
-// TODO(nweiz): Keep track of and display multiple errors so there's more
-// visibility into cascading errors.
 // TODO(nweiz): Add timeouts to scheduled tests.
 // TODO(nweiz): Add support for calling [schedule] while the schedule is already
 // running.
 // TODO(nweiz): Port the non-Pub-specific scheduled test libraries from Pub.
 /// A package for writing readable tests of asynchronous behavior.
 ///
 /// This package works by building up a queue of asynchronous tasks called a
 /// "schedule", then executing those tasks in order. This allows the tests to
 /// read like synchronous, linear code, despite executing asynchronously.
 ///
@@ skipping 170 matching lines @@
   testFn(description, () {
     var asyncDone = unittest.expectAsync0(() {});
     return currentSchedule.run(() {
       if (_setUpFn != null) _setUpFn();
       body();
     }).then((_) {
       // If we got here, the test completed successfully so tell unittest so.
       asyncDone();
     }).catchError((e) {
       if (e is ScheduleError) {
-        unittest.registerException(new ExpectException(e.toString()));
+        assert(e.schedule.errors.contains(e));
+        assert(e.schedule == currentSchedule);
+        unittest.registerException(e.schedule.errorString());
       } else if (e is AsyncError) {
         unittest.registerException(e.error, e.stackTrace);
       } else {
         unittest.registerException(e);
       }
     });
   });
 }
 
 /// Whether or not the tests currently being defined are in a group. This is
@@ skipping 75 matching lines @@
   unittest.ensureInitialized();
   unittest.wrapAsync = (f) {
     if (currentSchedule == null) {
       throw new StateError("Unexpected call to wrapAsync with no current "
           "schedule.");
     }
 
     return currentSchedule.wrapAsync(f);
   };
 }