Added another test for negative numerators

src/test/py/test_fractions.py

@@ -10,7 +10,10 @@ class fractions(unittest.TestCase):
         pass
 
     def test_dec_value_of_20_by_5_should_be_4(self):
-        self.assertEqual(frac_to_dec(20,5), 4)  # add assertion here
+        self.assertEqual(frac_to_dec(20,5), 4)
+
+    def test_dec_value_of_negative_20_by_5_should_be_negative_4(self):
+        self.assertEqual(frac_to_dec(-20,5), -4)
 
 
 if __name__ == '__main__':