Fix analyzer hints and warnings in test/.

test/lock_file_test.dart

 // Copyright (c) 2012, 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 lock_file_test;
 
 import 'dart:async';
 
 import 'package:pub/src/lock_file.dart';
 import 'package:pub/src/package.dart';
 import 'package:pub/src/pubspec.dart';
 import 'package:pub/src/source.dart';
 import 'package:pub/src/source_registry.dart';
 import 'package:pub_semver/pub_semver.dart';
 import 'package:test/test.dart';
 import 'package:yaml/yaml.dart';
 
-import 'test_pub.dart';
-
 class MockSource extends Source {
   final String name = 'mock';
 
   Future<List<PackageId>> doGetVersions(PackageRef ref) =>
       throw new UnsupportedError("Cannot get mock package versions.");
 
   Future<Pubspec> doDescribe(PackageId id) => throw new UnsupportedError(
       "Cannot describe mock packages.");
 
   Future get(PackageId id, String symlink) => throw new UnsupportedError(
@@ skipping 152 matching lines @@
 packages:
   foo:
     version: 1.2.3
     source: mock
     description: foo desc is bad
 ''', sources);
         }, throwsFormatException);
       });
 
       test("ignores extra stuff in file", () {
-        var lockFile = new LockFile.parse('''
+        new LockFile.parse('''
 extra:
   some: stuff
 packages:
   foo:
     bonus: not used
     version: 1.2.3
     source: mock
     description: foo desc
 ''', sources);
       });
@@ skipping 17 matching lines @@
           'bar': {
             'version': '3.2.1',
             'source': 'mock',
             'description': 'bar desc'
           }
         }
       }));
     });
   });
 }