diff --git a/lam/tests/lib/modules/bindDLZTest.php b/lam/tests/lib/modules/bindDLZTest.php
new file mode 100644
index 00000000..c9dfb8a6
--- /dev/null
+++ b/lam/tests/lib/modules/bindDLZTest.php
@@ -0,0 +1,36 @@
+<?php
+/*
+ This code is part of LDAP Account Manager (http://www.ldap-account-manager.org/)
+ Copyright (C) 2018  Roland Gruber
+ */
+
+if (is_readable('lam/lib/modules/bindDLZ.inc')) {
+
+	include_once 'lam/lib/baseModule.inc';
+	include_once 'lam/lib/modules.inc';
+	include_once 'lam/lib/modules/bindDLZ.inc';
+
+	/**
+	 * Checks the bindDLZ module.
+	 *
+	 * @author Roland Gruber
+	 */
+	class bindDLZTest extends PHPUnit_Framework_TestCase {
+
+		public function testIncreaseSerial() {
+			$this->assertEquals('1', bindDLZ::increaseSerial(''));
+			$this->assertEquals('4', bindDLZ::increaseSerial('3'));
+			$this->assertEquals('10', bindDLZ::increaseSerial('9'));
+			$date = new DateTime('now', new DateTimeZone('UTC'));
+			$dateStr = $date->format('Ymd');
+			$this->assertEquals($dateStr . '2', bindDLZ::increaseSerial($dateStr . '1'));
+			$this->assertEquals($dateStr . '06', bindDLZ::increaseSerial($dateStr . '05'));
+			$this->assertEquals($dateStr . '0010', bindDLZ::increaseSerial($dateStr . '0009'));
+			$this->assertEquals($dateStr . '100', bindDLZ::increaseSerial($dateStr . '99'));
+			$this->assertEquals($dateStr . '001', bindDLZ::increaseSerial('20010517003'));
+			$this->assertEquals('20990517004', bindDLZ::increaseSerial('20990517003'));
+		}
+
+	}
+
+}