Use package:testing for tools/gardening

tools/gardening/test/compare_failures_test.dart

 // Copyright (c) 2017, 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.
 
 /// Compares the test log of a build step with previous builds.
 ///
 /// Use this to detect flakiness of failures, especially timeouts.
 
 import 'dart:async';
 
 import 'package:args/args.dart';
 import 'package:expect/expect.dart';
 import 'package:gardening/src/bot.dart';
 import 'package:gardening/src/buildbot_structures.dart';
 import 'package:gardening/src/client.dart';
 import 'package:gardening/src/compare_failures_impl.dart';
 import 'package:gardening/src/util.dart';
 
 import 'test_client.dart';
 
-// TODO(johnniwinther): Use 'package:testing' to run all tests.
 main(List<String> args) async {
   ArgParser argParser = createArgParser();
   argParser.addFlag('force', abbr: 'f');
   ArgResults argResults = argParser.parse(args);
   processArgResults(argResults);
 
   await runSingleTests(argResults);
   await runGroupTests(argResults);
 }
 
@@ skipping 82 matching lines @@
   print('Testing single compare-failures: $testUri runCount=$runCount');
   Map<BuildUri, List<BuildResult>> buildResults =
       await loadBuildResults(bot, [testUri], runCount: runCount);
   print('- checking results for ${buildResults.keys}');
   if (LOG) {
     printBuildResultsSummary(buildResults, [testUri]);
   }
   Expect.equals(1, buildResults.length);
   testSingleResults(expectedResult, buildResults.values.first);
 }