Extract testing utilities into a separate package.

pkg/analysis_server/test/domain_completion_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.domain.completion;
 
 import 'package:analysis_server/src/analysis_server.dart';
 import 'package:analysis_server/src/constants.dart';
 import 'package:analysis_server/src/domain_completion.dart';
 import 'package:analysis_server/src/protocol.dart';
+import 'package:analysis_testing/mock_sdk.dart';
 import 'package:analyzer/file_system/memory_file_system.dart';
 import 'package:unittest/unittest.dart';
 
 import 'mocks.dart';
 
 main() {
   groupSep = ' | ';
 
   MockServerChannel serverChannel;
   MemoryResourceProvider resourceProvider;
@@ skipping 13 matching lines @@
     test('getSuggestions', () {
       var request = new Request('0', COMPLETION_GET_SUGGESTIONS);
       request.setParameter(FILE, null);
       request.setParameter(OFFSET, null);
       var response = handler.handleRequest(request);
       // TODO(brianwilkerson) implement
       //expect(response, isNull);
     });
   });
 }