Switch analysis_server to use 'package:test'.

pkg/analysis_server/test/domain_diagnostic_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.domain.diagnostic;
 
 import 'package:analysis_server/plugin/protocol/protocol.dart';
 import 'package:analysis_server/src/analysis_server.dart';
 import 'package:analysis_server/src/domain_diagnostic.dart';
 import 'package:analysis_server/src/plugin/server_plugin.dart';
 import 'package:analyzer/file_system/memory_file_system.dart';
 import 'package:analyzer/instrumentation/instrumentation.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/sdk.dart';
 import 'package:plugin/manager.dart';
 import 'package:plugin/plugin.dart';
-import 'package:unittest/unittest.dart';
+import 'package:test/test.dart';
 
 import 'mock_sdk.dart';
 import 'mocks.dart';
 import 'utils.dart';
 
 main() {
   AnalysisServer server;
   DiagnosticDomainHandler handler;
   MemoryResourceProvider resourceProvider;
 
@@ skipping 58 matching lines @@
     });
 
     test('getDiagnostics - (no root)', () async {
       var request = new DiagnosticGetDiagnosticsParams().toRequest('0');
       var response = handler.handleRequest(request);
       Map json = response.toJson()[Response.RESULT];
       expect(json['contexts'], hasLength(0));
     });
   });
 }