chore(PubSub): Adding GCPServiceAccount and AWSRoleArn class variables to pubsubTest

Author: cy-yun

pubsub/api/test/pubsubTest.php

@@ -17,6 +17,7 @@
 
 namespace Google\Cloud\Samples\PubSub;
 
+use Google\Auth\Credentials\ServiceAccountCredentials;
 use Google\Cloud\TestUtils\TestTrait;
 use Google\Cloud\TestUtils\ExecuteCommandTrait;
 use Google\Cloud\TestUtils\EventuallyConsistentTestTrait;
@@ -32,10 +33,17 @@ class PubSubTest extends TestCase
     use EventuallyConsistentTestTrait;
 
     private static $eodSubscriptionId;
+    private static $awsRoleArn = "arn:aws:iam::111111111111:role/fake-role-name";
+    private static $gcpServiceAccount;
 
     public static function setUpBeforeClass(): void
     {
         self::$eodSubscriptionId = 'test-eod-subscription-' . rand();
+        $serviceAccountPath = self::requireEnv('GOOGLE_APPLICATION_CREDENTIALS');
+        $serviceAccountCredentials = new ServiceAccountCredentials(
+            'https://www.googleapis.com/auth/cloud-platform',
+            $serviceAccountPath);
+        self::$gcpServiceAccount = $serviceAccountCredentials->getClientName();
     }
 
     public function testSubscriptionPolicy()