Properly set the exit code for failing tests run directly.

test/runner/runner_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.
 
 @TestOn("vm")
 
 import 'dart:io';
 import 'dart:math' as math;
 
 import 'package:path/path.dart' as p;
@@ skipping 267 matching lines @@
       expect(result.exitCode, equals(0));
     });
 
     test("directly", () {
       new File(p.join(_sandbox, "test.dart")).writeAsStringSync(_success);
       var result = _runDart([
         "--package-root=${p.join(packageDir, 'packages')}",
         "test.dart"
       ]);
       expect(result.stdout, contains("All tests passed!"));
+      expect(result.exitCode, equals(0));
     });
 
     // Regression test; this broke in 0.12.0-beta.9.
     test("on a file in a subdirectory", () {
       new Directory(p.join(_sandbox, "dir")).createSync();
       new File(p.join(_sandbox, "dir", "test.dart"))
           .writeAsStringSync(_success);
       var result = _runUnittest(["dir/test.dart"]);
       expect(result.exitCode, equals(0));
     });
@@ skipping 27 matching lines @@
       expect(result.exitCode, equals(1));
     });
 
     test("directly", () {
       new File(p.join(_sandbox, "test.dart")).writeAsStringSync(_failure);
       var result = _runDart([
         "--package-root=${p.join(packageDir, 'packages')}",
         "test.dart"
       ]);
       expect(result.stdout, contains("Some tests failed."));
+      expect(result.exitCode, isNot(equals(0)));
     });
   });
 
   test("runs tests even when a file fails to load", () {
     new File(p.join(_sandbox, "test.dart")).writeAsStringSync(_success);
     var result = _runUnittest(["test.dart", "nonexistent.dart"]);
     expect(result.stdout, contains("+1 -1: Some tests failed."));
     expect(result.exitCode, equals(1));
   });
 
@@ skipping 312 matching lines @@
       });
     });
   });
 }
 
 ProcessResult _runUnittest(List<String> args) =>
     runUnittest(args, workingDirectory: _sandbox);
 
 ProcessResult _runDart(List<String> args) =>
     runDart(args, workingDirectory: _sandbox);