extended test_alter_column_set_type to also test running migrations in reverse

Author: dantownsend

tests/apps/migrations/auto/test_migration_manager.py

@@ -515,12 +515,17 @@ def test_alter_column_set_type(self):
         )
 
         asyncio.run(manager.run())
-
         column_type_str = self.get_postgres_column_type(
             tablename="manager", column_name="name"
         )
         self.assertEqual(column_type_str, "TEXT")
 
+        asyncio.run(manager.run_backwards())
+        column_type_str = self.get_postgres_column_type(
+            tablename="manager", column_name="name"
+        )
+        self.assertEqual(column_type_str, "CHARACTER VARYING")
+
     @postgres_only
     def test_alter_column_set_length(self):
         """