Use package:testing for tools/gardening

tools/gardening/bin/find_shard.dart

 #!/usr/bin/env 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.
 
 // Translates a buildbot shard name to the corresponding column group name
 // on the buildbot site, such that it's easier to find the right column.
 //
 // Example: `bin/find_shard.dart precomp-linux-debug-x64-be`
 // prints `vm-precomp(5): precomp-linux-debug-x64-be`.
 
+import 'dart:async';
 import 'dart:io';
 import 'package:args/args.dart';
 import 'package:gardening/src/shard_data.dart';
 
 ArgParser createArgParser() {
   ArgParser argParser = new ArgParser(allowTrailingOptions: true);
   argParser.addFlag('help', help: "Help");
   return argParser;
 }
 
@@ skipping 25 matching lines @@
   print(argParser.usage);
 }
 
 bool shard_enabled(String shard) {
   if (shard.endsWith('-dev')) return INCLUDE_DEV;
   if (shard.endsWith('-stable')) return INCLUDE_STABLE;
   if (shard.endsWith('-integration')) return INCLUDE_INTEGRATION;
   return true;
 }
 
-main(List<String> args) async {
+Future main(List<String> args) async {
   ArgParser argParser = createArgParser();
   argParser.addFlag("include-dev",
       abbr: "d",
       defaultsTo: false,
       negatable: false,
       help: "Include shards named *-dev");
   argParser.addFlag("include-stable",
       abbr: "s",
       defaultsTo: false,
       negatable: false,
@@ skipping 21 matching lines @@
   for (String group in shardGroups.keys) {
     List<String> shardGroup = shardGroups[group];
     for (int i = 0; i < shardGroup.length; i++) {
       String shard = shardGroup[i];
       if (shard_enabled(shard) && shard.contains(arg)) {
         print("$group(${i+1}): $shard");
       }
     }
   }
 }