Switch analysis_server to use 'package:test'.

pkg/analysis_server/test/services/completion/dart/label_contributor_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.
 
 library test.services.completion.contributor.dart.label;
 
 import 'package:analysis_server/plugin/protocol/protocol.dart' as protocol
     show Element, ElementKind;
 import 'package:analysis_server/plugin/protocol/protocol.dart'
     hide Element, ElementKind;
 import 'package:analysis_server/src/protocol_server.dart';
 import 'package:analysis_server/src/provisional/completion/dart/completion_dart.dart';
 import 'package:analysis_server/src/services/completion/dart/label_contributor.dart';
+import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
-import 'package:unittest/unittest.dart';
 
 import '../../../utils.dart';
 import 'completion_contributor_util.dart';
 
 main() {
   initializeTestEnvironment();
-  defineReflectiveTests(LabelContributorTest);
+  defineReflectiveSuite(() {
+    defineReflectiveTests(LabelContributorTest);
+  });
 }
 
 @reflectiveTest
 class LabelContributorTest extends DartCompletionContributorTest {
   CompletionSuggestion assertSuggestLabel(String name,
       {int relevance: DART_RELEVANCE_DEFAULT,
       CompletionSuggestionKind kind: CompletionSuggestionKind.IDENTIFIER}) {
     CompletionSuggestion cs =
         assertSuggest(name, csKind: kind, relevance: relevance);
     expect(cs.returnType, isNull);
@@ skipping 284 matching lines @@
       break;
     foo: case 2:
       continue ^;
     case 3:
       break;
 ''');
     await computeSuggestions();
     assertSuggestLabel('foo');
   }
 }