feat: add basic db handler, for tracking counter values

more to come i'm sure, this is all i need so far

tests/db/test_handler.py

@@ -0,0 +1,64 @@
+# -*- coding: utf-8; -*-
+
+from unittest.mock import patch, MagicMock
+
+from wuttjamaican.testing import DataTestCase
+
+try:
+    import sqlalchemy as sa
+    from wuttjamaican.db import handler as mod
+except ImportError:
+    pass
+else:
+
+    class TestDatabaseHandler(DataTestCase):
+
+        def make_handler(self, **kwargs):
+            return mod.DatabaseHandler(self.config, **kwargs)
+
+        def test_next_counter_value_sqlite(self):
+            handler = self.make_handler()
+
+            # counter table should not exist yet
+            metadata = sa.MetaData()
+            metadata.reflect(self.session.bind)
+            self.assertNotIn('_counter_testing', metadata.tables)
+
+            # using sqlite as backend, should make table for counter
+            value = handler.next_counter_value(self.session, 'testing')
+            self.assertEqual(value, 1)
+
+            # counter table should exist now
+            metadata.reflect(self.session.bind)
+            self.assertIn('_counter_testing', metadata.tables)
+
+            # counter increments okay
+            value = handler.next_counter_value(self.session, 'testing')
+            self.assertEqual(value, 2)
+            value = handler.next_counter_value(self.session, 'testing')
+            self.assertEqual(value, 3)
+
+        def test_next_counter_value_postgres(self):
+            handler = self.make_handler()
+
+            # counter table should not exist
+            metadata = sa.MetaData()
+            metadata.reflect(self.session.bind)
+            self.assertNotIn('_counter_testing', metadata.tables)
+
+            # nb. we have to pretty much mock this out, can't really
+            # test true sequence behavior for postgres since tests are
+            # using sqlite backend.
+
+            # using postgres as backend, should use "sequence"
+            with patch.object(self.session.bind.url, 'get_dialect') as get_dialect:
+                get_dialect.return_value.name = 'postgresql'
+                with patch.object(self.session, 'execute') as execute:
+                    execute.return_value.scalar.return_value = 1
+                    value = handler.next_counter_value(self.session, 'testing')
+                    self.assertEqual(value, 1)
+                    execute.return_value.scalar.assert_called_once_with()
+
+            # counter table should still not exist
+            metadata.reflect(self.session.bind)
+            self.assertNotIn('_counter_testing', metadata.tables)

tests/test_app.py

@@ -448,6 +448,15 @@ app_title = WuttaTest
         auth = self.app.get_auth_handler()
         self.assertIsInstance(auth, AuthHandler)
 
+    def test_get_db_handler(self):
+        try:
+            from wuttjamaican.db.handler import DatabaseHandler
+        except ImportError:
+            pytest.skip("test not relevant without sqlalchemy")
+
+        db = self.app.get_db_handler()
+        self.assertIsInstance(db, DatabaseHandler)
+
     def test_get_email_handler(self):
         from wuttjamaican.email import EmailHandler