diff --git a/converter.py b/converter.py
index 5e9f16331250bb0738dc3bd89f8912425a7b4118..1d5eff48258d339da12cee00fa9dd6dd640c6911 100644
--- a/converter.py
+++ b/converter.py
@@ -163,6 +163,18 @@ class TestConverter(unittest.TestCase):
         res = self.c.convert(4000)
         self.assertEqual(res, "MMMM")
 
+    def test_convertThirty(self):
+        res = self.c.convert(30)
+        self.assertEqual(res, "XXX")
+
+    def test_convertNinety(self):
+        res = self.c.convert(90)
+        self.assertEqual(res, "XC")
+
+    def test_convertEmpty(self):
+        res = self.c.convert('')
+        self.assertEqual(res, "Bitte ganze Zahlen eingeben")
+