added a shim so coroutines can be mocked in python 3.7 tests

Author: dantownsend

tests/apps/migrations/auto/test_migration_manager.py

@@ -8,7 +8,7 @@
 
 from tests.example_app.tables import Manager
 from tests.base import DBTestCase
-from tests.base import postgres_only
+from tests.base import postgres_only, set_mock_return_value
 
 
 class TestMigrationManager(DBTestCase):
@@ -202,7 +202,7 @@ def test_drop_column(self, get_migration_managers: MagicMock):
         self.assertEqual(response, [{"id": 1}])
 
         # Reverse
-        get_migration_managers.return_value = [manager_1]
+        set_mock_return_value(get_migration_managers, [manager_1])
         asyncio.run(manager_2.run_backwards())
         response = self.run_sync("SELECT * FROM musician;")
         self.assertEqual(response, [{"id": 1, "name": ""}])
@@ -380,7 +380,7 @@ def test_drop_table(self, get_migration_managers: MagicMock):
         manager_2.drop_table(class_name="Musician", tablename="musician")
         asyncio.run(manager_2.run())
 
-        get_migration_managers.return_value = [manager_1]
+        set_mock_return_value(get_migration_managers, [manager_1])
 
         self.assertTrue(not self.table_exists("musician"))
 

tests/base.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 import typing as t
 from unittest import TestCase
+from unittest.mock import MagicMock
 
 import pytest
 
@@ -23,6 +24,22 @@
 )
 
 
+def set_mock_return_value(magic_mock: MagicMock, return_value: t.Any):
+    """
+    Python 3.8 has good support for mocking coroutines. For older versions,
+    we must set the return value to be an awaitable explicitly.
+    """
+    if magic_mock.__class__.__name__ == "AsyncMock":
+        # Python 3.8 and above
+        magic_mock.return_value = return_value
+    else:
+
+        async def coroutine(*args, **kwargs):
+            return return_value
+
+        magic_mock.return_value = coroutine()
+
+
 class DBTestCase(TestCase):
     """
     Using raw SQL where possible, otherwise the tests are too reliant on other