Use helper methods for running pub.

sdk/lib/_internal/pub/test/install/path/absolute_path_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS d.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 d.file.
 
 import 'package:pathos/path.dart' as path;
 import 'package:scheduled_test/scheduled_test.dart';
 
 import '../../../lib/src/io.dart';
 import '../../descriptor.dart' as d;
 import '../../test_pub.dart';
 
 main() {
   initConfig();
   integration('path dependency with absolute path', () {
     d.dir('foo', [
       d.libDir('foo'),
       d.libPubspec('foo', '0.0.1')
     ]).create();
 
     d.dir(appPath, [
       d.pubspec({
         "name": "myapp",
         "dependencies": {
           "foo": {"path": path.join(sandboxDir, "foo")}
         }
       })
     ]).create();
 
-    schedulePub(args: ["install"],
-        output: new RegExp(r"Dependencies installed!$"));
+    pubInstall();
 
     d.dir(packagesPath, [
       d.dir("foo", [
         d.file("foo.dart", 'main() => "foo";')
       ])
     ]).validate();
 
     // Move the packages directory and ensure the symlink still works. That
     // will validate that we actually created an absolute symlink.
     d.dir("moved").create();
     scheduleRename(packagesPath, "moved/packages");
 
     d.dir("moved/packages", [
       d.dir("foo", [
         d.file("foo.dart", 'main() => "foo";')
       ])
     ]).validate();
   });
 }