Add more tests to cover num2words/base.py

Signed-off-by: William José Moreno Reyes <williamjmorenor@gmail.com>

tests/test_base.py

@@ -32,3 +32,15 @@ def setUpClass(cls):
     def test_to_currency_not_implemented(self):
         with self.assertRaises(NotImplementedError):
             self.base.to_currency(Decimal('1.00'), currency='EUR')
+
+    def test_error_to_cardinal_float(self):
+        from num2words.base import Num2Word_Base
+        with self.assertRaises(TypeError):
+            Num2Word_Base.to_cardinal_float(9)
+        with self.assertRaises(TypeError):
+            Num2Word_Base.to_cardinal_float("a")
+
+    def test_error_merge(self):
+        from num2words.base import Num2Word_Base
+        with self.assertRaises(NotImplementedError):
+            Num2Word_Base.merge(1,2,3)