diff --git a/apps/user_ldap/lib/Jobs/Sync.php b/apps/user_ldap/lib/Jobs/Sync.php
index 179ba92312..17409cb8ca 100644
--- a/apps/user_ldap/lib/Jobs/Sync.php
+++ b/apps/user_ldap/lib/Jobs/Sync.php
@@ -34,11 +34,12 @@ use OCA\User_LDAP\LDAP;
 use OCA\User_LDAP\LogWrapper;
 use OCA\User_LDAP\Mapping\UserMapping;
 use OCA\User_LDAP\User\Manager;
-use OCA\User_LDAP\User_LDAP;
 use OCP\Image;
 use OCP\IServerContainer;
 
 class Sync extends TimedJob {
+	const MAX_INTERVAL = 12 * 60 * 60; // 12h
+	const MIN_INTERVAL = 30 * 60; // 30min
 	/** @var IServerContainer */
 	protected $c;
 	/** @var  Helper */
@@ -49,17 +50,13 @@ class Sync extends TimedJob {
 	protected $userManager;
 	/** @var UserMapping */
 	protected $mapper;
-	/** @var int */
-	protected $maxInterval = 12 * 60 * 60; // 12h
-	/** @var int */
-	protected $minInterval = 30 * 60; // 30min
 
 	public function __construct() {
 		$this->setInterval(
 			\OC::$server->getConfig()->getAppValue(
 				'user_ldap',
 				'background_sync_interval',
-				$this->minInterval
+				self::MIN_INTERVAL
 			)
 		);
 	}
@@ -75,9 +72,10 @@ class Sync extends TimedJob {
 		$minPagingSize = $this->getMinPagingSize();
 		$mappedUsers = $this->mapper->count();
 
-		$runsPerDay = ($minPagingSize === 0) ? $this->maxInterval : $mappedUsers / $minPagingSize;
+		$runsPerDay = ($minPagingSize === 0 || $mappedUsers === 0) ? self::MAX_INTERVAL
+			: $mappedUsers / $minPagingSize;
 		$interval = floor(24 * 60 * 60 / $runsPerDay);
-		$interval = min(max($interval, $this->minInterval), $this->maxInterval);
+		$interval = min(max($interval, self::MIN_INTERVAL), self::MAX_INTERVAL);
 
 		$this->c->getConfig()->setAppValue('user_ldap', 'background_sync_interval', $interval);
 	}
diff --git a/apps/user_ldap/tests/Jobs/SyncTest.php b/apps/user_ldap/tests/Jobs/SyncTest.php
new file mode 100644
index 0000000000..6b11c6145e
--- /dev/null
+++ b/apps/user_ldap/tests/Jobs/SyncTest.php
@@ -0,0 +1,130 @@
+<?php
+/**
+ * @copyright Copyright (c) 2017 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\Jobs;
+
+use OCA\User_LDAP\Helper;
+use OCA\User_LDAP\Jobs\Sync;
+use OCA\User_LDAP\LDAP;
+use OCA\User_LDAP\Mapping\UserMapping;
+use OCA\User_LDAP\User\Manager;
+use OCP\IConfig;
+use OCP\IServerContainer;
+use Test\TestCase;
+
+class SyncTest extends TestCase {
+
+	/** @var  array */
+	protected $arguments;
+	/** @var  IServerContainer|\PHPUnit_Framework_MockObject_MockObject */
+	protected $c;
+	/** @var  Helper|\PHPUnit_Framework_MockObject_MockObject */
+	protected $helper;
+	/** @var  LDAP|\PHPUnit_Framework_MockObject_MockObject */
+	protected $ldapWrapper;
+	/** @var  Manager|\PHPUnit_Framework_MockObject_MockObject */
+	protected $userManager;
+	/** @var  UserMapping|\PHPUnit_Framework_MockObject_MockObject */
+	protected $mapper;
+	/** @var  Sync */
+	protected $sync;
+
+	public function setUp() {
+		parent::setUp();
+
+		$this->c = $this->createMock(IServerContainer::class);
+		$this->helper = $this->createMock(Helper::class);
+		$this->ldapWrapper = $this->createMock(LDAP::class);
+		$this->userManager = $this->createMock(Manager::class);
+		$this->mapper = $this->createMock(UserMapping::class);
+
+		$this->arguments = [
+			'c' => $this->c,
+			'helper' => $this->helper,
+			'ldapWrapper' => $this->ldapWrapper,
+			'userManager' => $this->userManager,
+			'mapper' => $this->mapper,
+		];
+
+		$this->sync = new Sync();
+	}
+
+	public function intervalDataProvider() {
+		return [
+			[
+				0, 1000, 750
+			],
+			[
+				22,	0, 50
+			],
+			[
+				500, 500, 500
+			],
+			[
+				1357, 0, 0
+			],
+			[
+				421337, 2000, 3000
+			]
+		];
+	}
+
+	/**
+	 * @dataProvider intervalDataProvider
+	 */
+	public function testUpdateInterval($userCount, $pagingSize1, $pagingSize2) {
+		$config = $this->createMock(IConfig::class);
+		$config->expects($this->once())
+			->method('setAppValue')
+			->with('user_ldap', 'background_sync_interval', $this->anything())
+			->willReturnCallback(function($a, $k, $interval) {
+				$this->assertTrue($interval >= SYNC::MIN_INTERVAL);
+				$this->assertTrue($interval <= SYNC::MAX_INTERVAL);
+				return true;
+			});
+		$config->expects($this->atLeastOnce())
+			->method('getAppKeys')
+			->willReturn([
+				'blabla',
+				'ldap_paging_size',
+				's07blabla',
+				'installed',
+				's07ldap_paging_size'
+			]);
+		$config->expects($this->exactly(2))
+			->method('getAppValue')
+			->willReturnOnConsecutiveCalls($pagingSize1, $pagingSize2);
+
+		$this->c->expects($this->any())
+			->method('getConfig')
+			->willReturn($config);
+
+		$this->mapper->expects($this->atLeastOnce())
+			->method('count')
+			->willReturn($userCount);
+
+		$this->sync->setArgument($this->arguments);
+		$this->sync->updateInterval();
+	}
+
+}