Extract testing utilities into a separate package.

pkg/analyzer/test/index/store/separate_file_manager_test.dart

Index: pkg/analyzer/test/index/store/separate_file_manager_test.dart
diff --git a/pkg/analyzer/test/index/store/separate_file_manager_test.dart b/pkg/analyzer/test/index/store/separate_file_manager_test.dart
index e846d9b4657c31a8b5aaecf93642b5eb09d84a9e..810a918ec91f7a41f0a9d9ae9fee58b98f0f6220 100644
--- a/pkg/analyzer/test/index/store/separate_file_manager_test.dart
+++ b/pkg/analyzer/test/index/store/separate_file_manager_test.dart
@@ -6,12 +6,11 @@ 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 = ' | ';