diff --git a/py65/tests/utils/test_conversions.py b/py65/tests/utils/test_conversions.py
index 1d79527..4b780de 100644
--- a/py65/tests/utils/test_conversions.py
+++ b/py65/tests/utils/test_conversions.py
@@ -1,18 +1,28 @@
 import sys
 import unittest
-from py65.utils.conversions import itoa
+from py65.utils.conversions import itoa, convert_to_bin, convert_to_bcd
 
 
 class ConversionsTopLevelTests(unittest.TestCase):
     def test_itoa_decimal_output(self):
         self.assertEqual('10', itoa(10, base=10))
+        self.assertEqual('-10', itoa(-10, base=10))
 
     def test_itoa_hex_output(self):
         self.assertEqual('a', itoa(10, base=16))
+        self.assertEqual('-a', itoa(-10, base=16))
 
     def test_itoa_bin_output(self):
         self.assertEqual('1010', itoa(10, base=2))
+        self.assertEqual('-1010', itoa(-10, base=2))
 
+    def test_convert_to_bin(self):
+        self.assertEqual(0, convert_to_bin(0))
+        self.assertEqual(99, convert_to_bin(0x99))
+
+    def test_convert_to_bcd(self):
+        self.assertEqual(0, convert_to_bcd(0))
+        self.assertEqual(0x99, convert_to_bcd(99))
 
 def test_suite():
     return unittest.findTestCases(sys.modules[__name__])