Use helper methods for running pub.

sdk/lib/_internal/pub/test/install/path/relative_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 '../../../lib/src/exit_codes.dart' as exit_codes;
 import '../../descriptor.dart' as d;
 import '../../test_pub.dart';
 
 main() {
   initConfig();
   integration("can use relative path", () {
     d.dir("foo", [
       d.libDir("foo"),
       d.libPubspec("foo", "0.0.1")
     ]).create();
 
     d.dir(appPath, [
       d.pubspec({
         "name": "myapp",
         "dependencies": {
           "foo": {"path": "../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();
   });
 
   integration("path is relative to containing d.pubspec", () {
     d.dir("relative", [
@@ skipping 11 matching lines @@
 
     d.dir(appPath, [
       d.pubspec({
         "name": "myapp",
         "dependencies": {
           "foo": {"path": "../relative/foo"}
         }
       })
     ]).create();
 
-    schedulePub(args: ["install"],
-        output: new RegExp(r"Dependencies installed!$"));
+    pubInstall();
 
     d.dir(packagesPath, [
       d.dir("foo", [
         d.file("foo.dart", 'main() => "foo";')
       ]),
       d.dir("bar", [
         d.file("bar.dart", 'main() => "bar";')
       ])
     ]).validate();
   });
 }