add testing for cokelog stuff

src/squarepay/tests.py

 from django.test import TestCase
+from django.conf import settings
+from datetime import datetime
 
-# Create your tests here.
+from .cokelog import CokeLog
+
+class ParseCokeLog(TestCase):
+    def test_parse_cokelog(self):
+        fn = getattr(settings, 'COKELOG_PATH', None)
+        if fn is None:
+            return
+
+        cokelog = CokeLog()
+        self.assertFalse(cokelog.is_loaded())
+        cokelog.open()
+        self.assertTrue(cokelog.is_loaded())
+
+        self.assertIsInstance(cokelog.dispenses, dict)
+        for key, val in cokelog.dispenses.items():
+            self.assertIsInstance(val, (list, tuple))
+            for record in val:
+                self.assertIsInstance(record, dict)
+                self.assertTrue('by' in record)
+                self.assertTrue('item' in record)
+                self.assertIsInstance(record['date'], datetime)
+
+        n = len(cokelog.dispenses)
+        cokelog.reload()
+        self.assertTrue(n == len(cokelog.dispenses))