diff --git a/Tests/t_ldap_filter.py b/Tests/t_ldap_filter.py
index 9ba3f5a..2fe1f2f 100644
--- a/Tests/t_ldap_filter.py
+++ b/Tests/t_ldap_filter.py
@@ -15,12 +15,49 @@ class TestDN(unittest.TestCase):
     test ldap.functions
     """
 
-    def test_escape_filter_chars(self):
+    def test_escape_filter_chars_mode0(self):
         """
-        test function is_dn()
+        test function escape_filter_chars() with escape_mode=0
         """
-        self.assertEquals(escape_filter_chars(r'foobar'), 'foobar')
-        self.assertEquals(escape_filter_chars(r'foo\bar'), r'foo\5cbar')
+        self.assertEquals(
+            escape_filter_chars(r'foobar'),
+            'foobar'
+        )
+        self.assertEquals(
+            escape_filter_chars(r'foo\bar'),
+            r'foo\5cbar'
+        )
+        self.assertEquals(
+            escape_filter_chars(
+                r'foo\bar',
+                escape_mode=0
+            ),
+            r'foo\5cbar'
+        )
+
+    def test_escape_filter_chars_mode1(self):
+        """
+        test function escape_filter_chars() with escape_mode=1
+        """
+        self.assertEquals(
+            escape_filter_chars(
+                '\xc3\xa4\xc3\xb6\xc3\xbc\xc3\x84\xc3\x96\xc3\x9c\xc3\x9f',
+                escape_mode=1
+            ),
+            r'\c3\a4\c3\b6\c3\bc\c3\84\c3\96\c3\9c\c3\9f'
+        )
+
+    def test_escape_filter_chars_mode2(self):
+        """
+        test function escape_filter_chars() with escape_mode=2
+        """
+        self.assertEquals(
+            escape_filter_chars(
+                'foobar',
+                escape_mode=2
+            ),
+            r'\66\6f\6f\62\61\72'
+        )
 
 
 if __name__ == '__main__':