added transaction tests

Author: dantownsend

aragorm/engine/postgres.py

@@ -29,6 +29,9 @@ async def run(self):
             for query in self.queries:
                 await connection.execute(query.__str__())
 
+        # In case the transaction object gets reused:
+        self.queries = []
+
     def run_sync(self):
         return asyncio.run(self.run())
 

tests/engine/test_transaction.py

@@ -0,0 +1,48 @@
+from unittest import TestCase
+
+from ..example_project.tables import Pokemon, Trainer
+
+
+class TestTransaction(TestCase):
+
+    def test_error(self):
+        """
+        Make sure queries in a transaction aren't committed if a query fails.
+        """
+        transaction = Pokemon.Meta.db.transaction()
+        transaction.add(
+            Pokemon.create(),
+            Trainer.create(),
+            Pokemon.raw('MALFORMED QUERY ... SHOULD ERROR')
+        )
+        try:
+            transaction.run_sync()
+        except Exception:
+            pass
+        self.assertTrue(
+            not Pokemon.table_exists().run_sync()
+        )
+        self.assertTrue(
+            not Trainer.table_exists().run_sync()
+        )
+
+    def test_succeeds(self):
+        transaction = Pokemon.Meta.db.transaction()
+        transaction.add(
+            Pokemon.create(),
+            Trainer.create()
+        )
+        transaction.run_sync()
+
+        self.assertTrue(
+            Pokemon.table_exists().run_sync()
+        )
+        self.assertTrue(
+            Trainer.table_exists().run_sync()
+        )
+
+        transaction.add(
+            Pokemon.drop(),
+            Trainer.drop()
+        )
+        transaction.run_sync()