Refactor unittests

tests/compiler/dart2js/serialization/model_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 dart2js.serialization_model_test;
 
 import 'dart:async';
 import 'dart:io';
 import 'package:async_helper/async_helper.dart';
 import 'package:expect/expect.dart';
 import 'package:compiler/src/commandline_options.dart';
 import 'package:compiler/src/common/backend_api.dart';
 import 'package:compiler/src/common/names.dart';
 import 'package:compiler/src/common/resolution.dart';
 import 'package:compiler/src/compiler.dart';
 import 'package:compiler/src/dart_types.dart';
 import 'package:compiler/src/elements/elements.dart';
 import 'package:compiler/src/filenames.dart';
 import 'package:compiler/src/serialization/element_serialization.dart';
 import 'package:compiler/src/serialization/impact_serialization.dart';
 import 'package:compiler/src/serialization/json_serializer.dart';
 import 'package:compiler/src/serialization/serialization.dart';
 import 'package:compiler/src/serialization/equivalence.dart';
 import 'package:compiler/src/serialization/task.dart';
 import 'package:compiler/src/universe/world_impact.dart';
 import 'package:compiler/src/universe/class_set.dart';
 import 'package:compiler/src/universe/use.dart';
-import 'memory_compiler.dart';
-import 'serialization_helper.dart';
-import 'serialization_test_data.dart';
-import 'serialization_test_helper.dart';
+import '../memory_compiler.dart';
+import 'helper.dart';
+import 'test_data.dart';
+import 'test_helper.dart';
 
 main(List<String> args) {
   asyncTest(() async {
     Arguments arguments = new Arguments.from(args);
     String serializedData = await serializeDartCore(arguments: arguments);
     if (arguments.filename != null) {
       Uri entryPoint = Uri.base.resolve(nativeToUriPath(arguments.filename));
       await check(serializedData, entryPoint);
     } else {
       Uri entryPoint = Uri.parse('memory:main.dart');
@@ skipping 143 matching lines @@
 
     if (failOnUnfound || remaining.isNotEmpty) {
       Expect.fail(message);
     } else {
       print(message);
     }
   } else if (verbose) {
     print(message);
   }
 }