diff --git a/apps/user_ldap/lib/User/DeletedUsersIndex.php b/apps/user_ldap/lib/User/DeletedUsersIndex.php
index 9ec95a01b5..3473398f41 100644
--- a/apps/user_ldap/lib/User/DeletedUsersIndex.php
+++ b/apps/user_ldap/lib/User/DeletedUsersIndex.php
@@ -70,7 +70,7 @@ class DeletedUsersIndex {
 		$deletedUsers = $this->config->getUsersForUserValue(
 			'user_ldap', 'isDeleted', '1');
 
-		$userObjects = array();
+		$userObjects = [];
 		foreach($deletedUsers as $user) {
 			$userObjects[] = new OfflineUser($user, $this->config, $this->db, $this->mapping);
 		}
@@ -95,20 +95,20 @@ class DeletedUsersIndex {
 	 * @return bool
 	 */
 	public function hasUsers() {
-		if($this->deletedUsers === false) {
+		if(!is_array($this->deletedUsers)) {
 			$this->fetchDeletedUsers();
 		}
-		if(is_array($this->deletedUsers) && count($this->deletedUsers) > 0) {
-			return true;
-		}
-		return false;
+		return is_array($this->deletedUsers) && (count($this->deletedUsers) > 0);
 	}
 
 	/**
 	 * marks a user as deleted
+	 *
 	 * @param string $ocName
+	 * @throws \OCP\PreConditionNotMetException
 	 */
 	public function markUser($ocName) {
 		$this->config->setUserValue($ocName, 'user_ldap', 'isDeleted', '1');
+		$this->deletedUsers = null;
 	}
 }
diff --git a/apps/user_ldap/tests/User/DeletedUsersIndexTest.php b/apps/user_ldap/tests/User/DeletedUsersIndexTest.php
new file mode 100644
index 0000000000..b3cf076e97
--- /dev/null
+++ b/apps/user_ldap/tests/User/DeletedUsersIndexTest.php
@@ -0,0 +1,118 @@
+<?php
+/**
+ * @copyright Copyright (c) 2018 Arthur Schiwon <blizzz@arthur-schiwon.de>
+ *
+ * @author Arthur Schiwon <blizzz@arthur-schiwon.de>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace OCA\User_LDAP\Tests\User;
+
+use OCA\User_LDAP\Mapping\UserMapping;
+use OCA\User_LDAP\User\DeletedUsersIndex;
+use OCP\IConfig;
+use OCP\IDBConnection;
+
+/**
+ * Class DeletedUsersIndexTest
+ *
+ * @group DB
+ *
+ * @package OCA\User_LDAP\Tests\User
+ */
+class DeletedUsersIndexTest extends \Test\TestCase {
+	/** @var DeletedUsersIndex */
+	protected $dui;
+
+	/** @var IConfig */
+	protected $config;
+
+	/** @var IDBConnection */
+	protected $db;
+
+	/** @var UserMapping|\PHPUnit_Framework_MockObject_MockObject */
+	protected $mapping;
+
+	public function setUp() {
+		parent::setUp();
+
+		// no mocks for those as tests go against DB
+		$this->config = \OC::$server->getConfig();
+		$this->db = \OC::$server->getDatabaseConnection();
+
+		$this->mapping = $this->createMock(UserMapping::class);
+
+		$this->dui = new DeletedUsersIndex($this->config, $this->db, $this->mapping);
+	}
+
+	public function tearDown() {
+		$this->config->deleteAppFromAllUsers('user_ldap');
+		return parent::tearDown();
+	}
+
+	public function testMarkAndFetchUser() {
+		$uids = [
+			'cef3775c-71d2-48eb-8984-39a4051b0b95',
+			'8c4bbb40-33ed-42d0-9b14-85b0ab76c1cc',
+		];
+
+		// ensure test works on a pristine state
+		$this->assertFalse($this->dui->hasUsers());
+
+		$this->dui->markUser($uids[0]);
+
+		$this->assertTrue($this->dui->hasUsers());
+
+		$this->dui->markUser($uids[1]);
+
+		$deletedUsers = $this->dui->getUsers();
+		$this->assertSame(2, count($deletedUsers));
+
+		// ensure the different uids were used
+		foreach($deletedUsers as $deletedUser) {
+			$this->assertTrue(in_array($deletedUser->getOCName(), $uids));
+			$i = array_search($deletedUser->getOCName(), $uids);
+			$this->assertNotFalse($i);
+			unset($uids[$i]);
+		}
+		$this->assertEmpty($uids);
+	}
+
+	public function testUnmarkUser() {
+		$uids = [
+			'22a162c7-a9ee-487c-9f33-0563795583fb',
+			'1fb4e0da-4a75-47f3-8fa7-becc7e35c9c5',
+		];
+
+		// we know this works, because of "testMarkAndFetchUser"
+		$this->dui->markUser($uids[0]);
+		// this returns a working instance of OfflineUser
+		$testUser = $this->dui->getUsers()[0];
+		$testUser->unmark();
+
+		// the DUI caches the users, to clear mark someone else
+		$this->dui->markUser($uids[1]);
+
+		$deletedUsers = $this->dui->getUsers();
+		foreach ($deletedUsers as $deletedUser) {
+			$this->assertNotSame($testUser->getOCName(), $deletedUser->getOCName());
+		}
+	}
+
+
+}