diff --git a/lib/private/Share/Share.php b/lib/private/Share/Share.php
index b9accda728..f6da19f3bb 100644
--- a/lib/private/Share/Share.php
+++ b/lib/private/Share/Share.php
@@ -45,6 +45,8 @@ namespace OC\Share;
 use OC\Files\Filesystem;
 use OCA\FederatedFileSharing\DiscoveryManager;
 use OCP\DB\QueryBuilder\IQueryBuilder;
+use OCP\ILogger;
+use OCP\IUserManager;
 use OCP\IUserSession;
 use OCP\IDBConnection;
 use OCP\IConfig;
@@ -128,19 +130,35 @@ class Share extends Constants {
 	 * Find which users can access a shared item
 	 * @param string $path to the file
 	 * @param string $ownerUser owner of the file
+	 * @param IUserManager $userManager
+	 * @param ILogger $logger
 	 * @param boolean $includeOwner include owner to the list of users with access to the file
 	 * @param boolean $returnUserPaths Return an array with the user => path map
 	 * @param boolean $recursive take all parent folders into account (default true)
 	 * @return array
 	 * @note $path needs to be relative to user data dir, e.g. 'file.txt'
 	 *       not '/admin/data/file.txt'
+	 * @throws \OC\User\NoUserException
 	 */
-	public static function getUsersSharingFile($path, $ownerUser, $includeOwner = false, $returnUserPaths = false, $recursive = true) {
-		$userManager = \OC::$server->getUserManager();
+	public static function getUsersSharingFile($path,
+											   $ownerUser,
+											   IUserManager $userManager,
+											   ILogger $logger,
+											   $includeOwner = false,
+											   $returnUserPaths = false,
+											   $recursive = true) {
 		$userObject = $userManager->get($ownerUser);
 
 		if (is_null($userObject)) {
-			\OCP\Util::writeLog('files', ' Backends provided no user object for ' . $ownerUser, \OCP\Util::ERROR);
+			$logger->error(
+				sprintf(
+					'Backends provided no user object for %s',
+					$ownerUser
+				),
+				[
+					'app' => 'files',
+				]
+			);
 			throw new \OC\User\NoUserException('Backends provided no user object');
 		}
 
diff --git a/lib/public/Share.php b/lib/public/Share.php
index bc7aa828f6..ec3a7c8db1 100644
--- a/lib/public/Share.php
+++ b/lib/public/Share.php
@@ -89,7 +89,15 @@ class Share extends \OC\Share\Constants {
 	 * @since 5.0.0 - $recursive was added in 9.0.0
 	 */
 	public static function getUsersSharingFile($path, $ownerUser, $includeOwner = false, $returnUserPaths = false, $recursive = true) {
-		return \OC\Share\Share::getUsersSharingFile($path, $ownerUser, $includeOwner, $returnUserPaths, $recursive);
+		return \OC\Share\Share::getUsersSharingFile(
+			$path,
+			$ownerUser,
+			\OC::$server->getUserManager(),
+			\OC::$server->getLogger(),
+			$includeOwner,
+			$returnUserPaths,
+			$recursive
+		);
 	}
 
 	/**
diff --git a/tests/lib/Files/FilesystemTest.php b/tests/lib/Files/FilesystemTest.php
index 04eafc99f3..dd4785ecf0 100644
--- a/tests/lib/Files/FilesystemTest.php
+++ b/tests/lib/Files/FilesystemTest.php
@@ -79,7 +79,6 @@ class FilesystemTest extends \Test\TestCase {
 
 	protected function setUp() {
 		parent::setUp();
-		\OC_User::clearBackends();
 		$userBackend = new \Test\Util\User\Dummy();
 		$userBackend->createUser(self::TEST_FILESYSTEM_USER1, self::TEST_FILESYSTEM_USER1);
 		$userBackend->createUser(self::TEST_FILESYSTEM_USER2, self::TEST_FILESYSTEM_USER2);
@@ -94,7 +93,6 @@ class FilesystemTest extends \Test\TestCase {
 
 		$this->logout();
 		$this->invokePrivate('\OC\Files\Filesystem', 'normalizedPathCache', [null]);
-		\OC_User::clearBackends();
 		parent::tearDown();
 	}
 
diff --git a/tests/lib/Share/ShareTest.php b/tests/lib/Share/ShareTest.php
index 6328952984..d550ba158a 100644
--- a/tests/lib/Share/ShareTest.php
+++ b/tests/lib/Share/ShareTest.php
@@ -20,6 +20,9 @@
 */
 
 namespace Test\Share;
+use OC\Share\Share;
+use OCP\ILogger;
+use OCP\IUserManager;
 
 /**
  * Class Test_Share
@@ -1631,6 +1634,31 @@ class ShareTest extends \Test\TestCase {
 			$this->assertEquals('Sharing failed, because the user ' . $this->user1 . ' is the original sharer', $e->getMessage());
 		}
 	}
+
+	/**
+	 * @expectedException \OC\User\NoUserException
+	 * @expectedExceptionMessage Backends provided no user object
+	 */
+	public function testGetUsersSharingFileWithException() {
+		$userManager = $this->createMock(IUserManager::class);
+		$logger = $this->createMock(ILogger::class);
+		$userManager
+			->expects($this->once())
+			->method('get')
+			->with('test')
+			->willReturn(null);
+		$logger
+			->expects($this->once())
+			->method('error')
+			->with(
+				'Backends provided no user object for test',
+				[
+					'app' => 'files',
+				]
+			);
+
+		Share::getUsersSharingFile('/my/file/path', 'test', $userManager, $logger);
+	}
 }
 
 class DummyShareClass extends \OC\Share\Share {
diff --git a/tests/lib/TestCase.php b/tests/lib/TestCase.php
index 1ca896e091..61372d4ae9 100644
--- a/tests/lib/TestCase.php
+++ b/tests/lib/TestCase.php
@@ -273,9 +273,6 @@ abstract class TestCase extends \PHPUnit_Framework_TestCase {
 		self::tearDownAfterClassCleanStrayHooks();
 		self::tearDownAfterClassCleanStrayLocks();
 
-		\OC_User::clearBackends();
-		\OC_User::useBackend('dummy');
-
 		parent::tearDownAfterClass();
 	}