Add simple Balance test for demonstration

Author: epels

tests/__init__.py

@@ -0,0 +1,23 @@
+import unittest
+from messagebird import Client
+
+try:
+    from unittest.mock import Mock
+except ImportError:
+    # mock was added to unittest in Python 3.3, but was an external library
+    # before.
+    from mock import Mock
+
+
+class TestBalance(unittest.TestCase):
+
+    def test_balance(self):
+        http_client = Mock()
+        http_client.request.return_value = '{"payment": "prepaid","type": "credits","amount": 9.2}'
+
+        balance = Client('', http_client).balance()
+
+        http_client.request.assert_called_once_with('balance', 'GET', None)
+
+        self.assertEqual('prepaid', balance.payment)
+        self.assertEqual('credits', balance.type)