Add a --reporter flag and expose the expanded reporter.

test/frontend/expect_async_test.dart

 // Copyright (c) 2015, 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.
 
 import 'package:test/src/backend/state.dart';
 import 'package:test/test.dart';
 
 import '../utils.dart';
 
 void main() {
@@ skipping 12 matching lines @@
 
     test("1", () {
       var callbackRun = false;
       return runTestBody(() {
         expectAsync((arg) {
           expect(arg, equals(1));
           callbackRun = true;
         })(1);
       }).then((liveTest) {
         expectTestPassed(liveTest);
-        expect(callbackRun, isTrue);
+        expect(callbackRun, isFalse);

[kevmoo, 2015/04/23 00:13:14]

sure? this failed for me.

[nweiz, 2015/04/23 00:15:52]

Done.

       });
     });
 
     test("2", () {
       var callbackRun = false;
       return runTestBody(() {
         expectAsync((arg1, arg2) {
           expect(arg1, equals(1));
           expect(arg2, equals(2));
           callbackRun = true;
         })(1, 2);
       }).then((liveTest) {
         expectTestPassed(liveTest);
-        expect(callbackRun, isTrue);
+        expect(callbackRun, isFalse);

[kevmoo, 2015/04/23 00:13:14]

ditto

[nweiz, 2015/04/23 00:15:52]

Done.

       });
     });
 
     test("3", () {
       var callbackRun = false;
       return runTestBody(() {
         expectAsync((arg1, arg2, arg3) {
           expect(arg1, equals(1));
           expect(arg2, equals(2));
           expect(arg3, equals(3));
@@ skipping 261 matching lines @@
           caughtError = true;
         }
       }).then((liveTest) {
         expectTestFailed(liveTest, 'oh no');
         expect(returnValue, isNull);
         expect(caughtError, isFalse);
       });
     });
   });
 }