Extract testing utilities into a separate package.

pkg/analyzer/test/index/store/separate_file_manager_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.engine.src.index.store.separate_file_mananer;
 
 import 'dart:io';
 
+import 'package:analysis_testing/reflective_tests.dart';
+import 'package:analyzer/src/index/store/separate_file_manager.dart';
 import 'package:path/path.dart';
 import 'package:unittest/unittest.dart';
 
-import '../../reflective_tests.dart';
-import 'package:analyzer/src/index/store/separate_file_manager.dart';
-
 
 main() {
   groupSep = ' | ';
   group('SeparateFileManager', () {
     runReflectiveTests(_SeparateFileManagerTest);
   });
 }
 
 
 @ReflectiveTestCase()
@@ skipping 43 matching lines @@
           expect(bytes, isNull);
         });
       });
     });
   }
 
   bool _existsSync(String name) {
     return new File(join(tempDir.path, name)).existsSync();
   }
 }