Extract testing utilities into a separate package.

pkg/analyzer/test/index/store/codec_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.codec;
 
+import 'package:analysis_testing/mocks.dart';
+import 'package:analysis_testing/reflective_tests.dart';
 import 'package:analyzer/index/index.dart';
 import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/index/store/codec.dart';
 import 'package:typed_mock/typed_mock.dart';
 import 'package:unittest/unittest.dart';
 
-import '../../reflective_tests.dart';
-import 'typed_mocks.dart';
-
 
 main() {
   groupSep = ' | ';
   group('ContextCodec', () {
     runReflectiveTests(_ContextCodecTest);
   });
   group('ElementCodec', () {
     runReflectiveTests(_ElementCodecTest);
   });
   group('RelationshipCodec', () {
@@ skipping 142 matching lines @@
 class _StringCodecTest {
   StringCodec codec = new StringCodec();
 
   void test_all() {
     int idA = codec.encode('aaa');
     int idB = codec.encode('bbb');
     expect(codec.decode(idA), 'aaa');
     expect(codec.decode(idB), 'bbb');
   }
 }