diff --git a/ucs-school-import/modules/ucsschool/importer/utils/username_handler.py b/ucs-school-import/modules/ucsschool/importer/utils/username_handler.py
index 5f07ab5..7de2acd 100644
--- a/ucs-school-import/modules/ucsschool/importer/utils/username_handler.py
+++ b/ucs-school-import/modules/ucsschool/importer/utils/username_handler.py
@@ -1,3 +1,4 @@
+#!/usr/bin/python2.7
 # -*- coding: utf-8 -*-
 #
 # Univention UCS@school
@@ -96,6 +97,43 @@ class UsernameHandler(object):
 
 		:param name: str: username, possibly a template
 		:return: str: unique username
+
+		>>> UsernameHandler(20).format_username('Max.Mustermann')
+		'Max.Mustermann'
+		>>> UsernameHandler(20).format_username('.')   # doctest: +IGNORE_EXCEPTION_DETAIL
+		Traceback (most recent call last):
+		...
+		FormatError:
+		>>> UsernameHandler(20).format_username('.Max.Mustermann.')
+		'Max.Mustermann'
+		>>> UsernameHandler(4).format_username('Max.Mustermann')
+		'M'
+		>>> for c in '\x01\x00\x03\x02\x05\x04\x07\x06\t\x08\x0b\n\r\x0c\x0f\x0e\x11\x10\x13\x12\x15\x14\x17\x16\x19\x18\x1b\x1a\x1d\x1c\x1f\x1e! #"%$\'&)(+*-,/;:=<?>@[]\\_^`{}|\x7f~':
+		...  assert 'Max' == UsernameHandler(20).format_username('Ma%sx' % (c,))
+		...
+		>>> UsernameHandler(20).format_username('Max.Mustermann12.4567890')
+		'Max.Mustermann12'
+		>>> for c in '.1032547698ACBEDGFIHKJMLONQPSRUTWVYXZacbedgfihkjmlonqpsrutwvyxz':
+		...  assert 'Ma%sx' % (c,) == UsernameHandler(20).format_username('Ma%sx' % (c,))
+		...
+		>>> UsernameHandler(20).format_username('Max[Muster]Mann')
+		'MaxMusterMann'
+		>>> UsernameHandler(20).format_username('Max[ALWAYSCOUNTER].Mustermann')
+		'Max1.Mustermann'
+		>>> UsernameHandler(20).format_username('Max[ALWAYSCOUNTER].Mustermann')
+		'Max2.Mustermann'
+		>>> UsernameHandler(20).format_username('Max[ALWAYSCOUNTER].Mustermann')
+		'Max3.Mustermann'
+		>>> UsernameHandler(20).format_username('Max[COUNTER2].Mustermann')
+		'Max4.Mustermann'
+		>>> UsernameHandler(20).format_username('Maria[ALWAYSCOUNTER].Musterfrau')
+		'Maria1.Musterfrau'
+		>>> UsernameHandler(20).format_username('Moritz[COUNTER2]')
+		'Moritz'
+		>>> UsernameHandler(20).format_username('Moritz[COUNTER2]')
+		'Moritz2'
+		>>> for i, c in enumerate('\x01\x00\x03\x02\x05\x04\x07\x06\t\x08\x0b\n\r\x0c\x0f\x0e\x11\x10\x13\x12\x15\x14\x17\x16\x19\x18\x1b\x1a\x1d\x1c\x1f\x1e! #"%$\'&)(+*-,/;:=<?>@\\_^`{}|\x7f~', 1):
+		...  assert 'Foo%d' % (i) == UsernameHandler(20).format_username('Fo%so[ALWAYSCOUNTER]' % (c,))
 		"""
 		assert isinstance(name, basestring)
 		ori_name = name
@@ -205,3 +243,8 @@ class UsernameHandler(object):
 			num = first_time
 			self.add_to_ldap(name_base, "2")
 		return num
+
+
+if __name__ == '__main__':
+	import doctest
+	doctest.testmod()