fix(tests): Address Copilot review feedback on S3 encryption tests

- Guard $config['class'] with null coalescing in setUpBeforeClass() to
  avoid PHP notice when objectstore is configured without a 'class' key
- Remove unused $rootStorage property and unwrapping loop in setUp()
  (was assigned but never referenced in any test method)
- Chain previous exception in getObjectUrn() throw to preserve stack trace

Signed-off-by: Stephen Cuppett <steve@cuppett.com>

Author: cuppett

tests/lib/Files/ObjectStore/S3EncryptionMigrationTest.php

@@ -56,7 +56,7 @@ public static function setUpBeforeClass(): void {
 		parent::setUpBeforeClass();
 
 		$config = Server::get(IConfig::class)->getSystemValue('objectstore');
-		if (!is_array($config) || $config['class'] !== S3::class) {
+		if (!is_array($config) || ($config['class'] ?? null) !== S3::class) {
 			self::markTestSkipped('S3 primary storage not configured');
 		}
 	}

tests/lib/Files/ObjectStore/S3EncryptionTest.php

@@ -9,7 +9,6 @@
 
 namespace Test\Files\ObjectStore;
 
-use OC\Files\ObjectStore\ObjectStoreStorage;
 use OC\Files\ObjectStore\S3;
 use OCP\IConfig;
 use OCP\Server;
@@ -51,15 +50,12 @@ class S3EncryptionTest extends \Test\TestCase {
 	/** @var array */
 	private $s3Config;
 
-	/** @var ObjectStoreStorage */
-	private $rootStorage;
-
 	public static function setUpBeforeClass(): void {
 		parent::setUpBeforeClass();
 
 		// Check if S3 primary storage is configured
 		$config = Server::get(IConfig::class)->getSystemValue('objectstore');
-		if (!is_array($config) || $config['class'] !== S3::class) {
+		if (!is_array($config) || ($config['class'] ?? null) !== S3::class) {
 			self::markTestSkipped('S3 primary storage not configured. Configure objectstore in config.php to run these tests.');
 		}
 	}
@@ -88,15 +84,6 @@ protected function setUp(): void {
 
 		// Get the view for the user
 		$this->view = new \OC\Files\View('/' . self::TEST_USER . '/files');
-
-		// Get the root ObjectStoreStorage (without wrapper) to check S3 sizes
-		$mount = \OC\Files\Filesystem::getMountManager()->find('/' . self::TEST_USER . '/files');
-		$this->rootStorage = $mount->getStorage();
-
-		// Unwrap to get the actual ObjectStoreStorage if it's wrapped
-		while ($this->rootStorage instanceof \OC\Files\Storage\Wrapper\Wrapper) {
-			$this->rootStorage = $this->rootStorage->getWrapperStorage();
-		}
 	}
 
 	protected function tearDown(): void {
@@ -143,7 +130,7 @@ private function getObjectUrn(string $path): string {
 			// URN format: urn:oid:{fileId}
 			return 'urn:oid:' . $fileId;
 		} catch (\Exception $e) {
-			throw new \Exception("File not found: $path - " . $e->getMessage());
+			throw new \Exception("File not found: $path - " . $e->getMessage(), 0, $e);
 		}
 	}