Use helper methods for running pub.

sdk/lib/_internal/pub/test/install/git/check_out_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 pub_tests;
 
 import 'dart:io';
 
 import '../../descriptor.dart' as d;
 import '../../test_pub.dart';
 
 main() {
   initConfig();
   integration('checks out a package from Git', () {
     ensureGit();
 
     d.git('foo.git', [
       d.libDir('foo'),
       d.libPubspec('foo', '1.0.0')
     ]).create();
 
     d.appDir([{"git": "../foo.git"}]).create();
 
-    schedulePub(args: ['install'],
-        output: new RegExp(r"Dependencies installed!$"));
+    pubInstall();
 
     d.dir(cachePath, [
       d.dir('git', [
         d.dir('cache', [d.gitPackageRepoCacheDir('foo')]),
         d.gitPackageRevisionCacheDir('foo')
       ])
     ]).validate();
 
     d.dir(packagesPath, [
       d.dir('foo', [
         d.file('foo.dart', 'main() => "foo";')
       ])
     ]).validate();
   });
 }