Switch analysis_server to use 'package:test'.

pkg/analysis_server/test/services/completion/dart/imported_reference_contributor_test.dart

 // Copyright (c) 2014, 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.imported_ref;
 
 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/imported_reference_contributor.dart';
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source.dart';
+import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
-import 'package:unittest/unittest.dart';
 
 import '../../../abstract_context.dart';
 import '../../../utils.dart';
 import 'completion_contributor_util.dart';
 
 main() {
   initializeTestEnvironment();
-  defineReflectiveTests(ImportedReferenceContributorTest);
+  defineReflectiveSuite(() {
+    defineReflectiveTests(ImportedReferenceContributorTest);
+  });
 }
 
 @reflectiveTest
 class ImportedReferenceContributorTest extends DartCompletionContributorTest {
   @override
   bool get isNullExpectedReturnTypeConsideredDynamic => false;
 
   @override
   DartCompletionContributor createContributor() {
     return new ImportedReferenceContributor();
@@ skipping 4467 matching lines @@
     assertNotSuggested('foo2');
     assertNotSuggested('bar2');
     assertNotSuggested('_B');
     assertNotSuggested('Y');
     assertNotSuggested('C');
     assertNotSuggested('f');
     assertNotSuggested('x');
     assertNotSuggested('e');
   }
 }