setUp/tearDown may be called repeatedly in a group.

lib/src/backend/declarer.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.
 
 library test.backend.declarer;
 
 import 'dart:collection';
 
 import '../frontend/timeout.dart';
 import 'group.dart';
@@ skipping 28 matching lines @@
 
     var group = _group;
     _tests.add(new LocalTest(description, metadata, () {
       // TODO(nweiz): It might be useful to throw an error here if a test starts
       // running while other tests from the same declarer are also running,
       // since they might share closurized state.
 
       // TODO(nweiz): Use async/await here once issue 23497 has been fixed in
       // two stable versions.
       return Invoker.current.waitForOutstandingCallbacks(() {
-        return group.runSetUp().then((_) => body());
-      }).then((_) => group.runTearDown());
+        return group.runSetUps().then((_) => body());
+      }).then((_) => group.runTearDowns());
     }));
   }
 
   /// Creates a group of tests.
   void group(String description, void body(), {String testOn,
       Timeout timeout, skip, Map<String, dynamic> onPlatform}) {
     var oldGroup = _group;
 
     var metadata = new Metadata.parse(
         testOn: testOn, timeout: timeout, skip: skip, onPlatform: onPlatform);
 
     // Don' load the tests for a skipped group.
     if (metadata.skip) {
       _tests.add(new LocalTest(description, metadata, () {}));
       return;
     }
 
     _group = new Group(oldGroup, description, metadata);
     try {
       body();
     } finally {
       _group = oldGroup;
     }
   }
 
   /// Registers a function to be run before tests.
   void setUp(callback()) {
-    if (_group.setUp != null) {
-      throw new StateError("setUp() may not be called multiple times for the "
-          "same group.");
-    }
-
-    _group.setUp = callback;
+    _group.setUps.add(callback);
   }
 
   /// Registers a function to be run after tests.
   void tearDown(callback()) {
-    if (_group.tearDown != null) {
-      throw new StateError("tearDown() may not be called multiple times for "
-          "the same group.");
-    }
-
-    _group.tearDown = callback;
+    _group.tearDowns.add(callback);
   }
 }