Add tests

setup.py

@@ -118,7 +118,9 @@ CONDITIONAL_REQUIREMENTS["mypy"] = [
 # Tests assume that all optional dependencies are installed.
 #
 # parameterized_class decorator was introduced in parameterized 0.7.0
-CONDITIONAL_REQUIREMENTS["test"] = ["parameterized>=0.7.0"]
+#
+# We use `mock` library as that backports `AsyncMock` to Python 3.6
+CONDITIONAL_REQUIREMENTS["test"] = ["parameterized>=0.7.0", "mock>=4.0.0"]
 
 CONDITIONAL_REQUIREMENTS["dev"] = (
     CONDITIONAL_REQUIREMENTS["lint"]

tests/storage/test_background_update.py

@@ -1,6 +1,11 @@
-from unittest.mock import Mock
+from mock import AsyncMock, Mock
 
-from synapse.storage.background_updates import BackgroundUpdater
+from twisted.internet.defer import Deferred, ensureDeferred
+
+from synapse.storage.background_updates import (
+    BackgroundUpdateController,
+    BackgroundUpdater,
+)
 
 from tests import unittest
 
@@ -79,3 +84,71 @@ class BackgroundUpdateTestCase(unittest.HomeserverTestCase):
         result = self.get_success(self.updates.do_next_background_update(False))
         self.assertTrue(result)
         self.assertFalse(self.update_handler.called)
+
+
+class BackgroundUpdateControllerTestCase(unittest.HomeserverTestCase):
+    def prepare(self, reactor, clock, homeserver):
+        self.updates: BackgroundUpdater = self.hs.get_datastore().db_pool.updates
+        # the base test class should have run the real bg updates for us
+        self.assertTrue(
+            self.get_success(self.updates.has_completed_background_updates())
+        )
+
+        self.update_deferred = Deferred()
+        self.update_handler = Mock(return_value=self.update_deferred)
+        self.updates.register_background_update_handler(
+            "test_update", self.update_handler
+        )
+
+        self._controller_ctx_mgr = AsyncMock(name="_controller_ctx_mgr")
+        self._controller = AsyncMock(BackgroundUpdateController)
+        self._controller.run_update.return_value = self._controller_ctx_mgr
+
+        self.updates.register_update_controller(self._controller)
+
+    def test_controller(self):
+        store = self.hs.get_datastore()
+        self.get_success(
+            store.db_pool.simple_insert(
+                "background_updates",
+                values={"update_name": "test_update", "progress_json": "{}"},
+            )
+        )
+
+        default_batch_size = 100
+
+        # Set up the return values of the controller.
+        enter_defer = Deferred()
+        self._controller_ctx_mgr.__aenter__ = Mock(return_value=enter_defer)
+        self._controller.default_batch_size.return_value = default_batch_size
+        self._controller.min_batch_size.return_value = default_batch_size
+
+        # Start the background update.
+        do_update_d = ensureDeferred(self.updates.do_next_background_update(True))
+
+        self.pump()
+
+        # `run_update` should have been called, but the update handler won't be
+        # called until the `enter_defer` (returned by `__aenter__`) is resolved.
+        self._controller.run_update.assert_called_once_with(
+            update_name="test_update",
+            database_name="master",
+            oneshot=False,
+        )
+        self.assertFalse(do_update_d.called)
+        self.assertFalse(self.update_deferred.called)
+
+        # Resolving the `enter_defer` should call the update handler, which then
+        # blocks.
+        enter_defer.callback(100)
+        self.pump()
+        self.update_handler.assert_called_once_with({}, default_batch_size)
+        self.assertFalse(self.update_deferred.called)
+        self._controller_ctx_mgr.__aexit__.assert_not_awaited()
+
+        # Resolving the update handler deferred should cause the
+        # `do_next_background_update` to finish and return
+        self.update_deferred.callback(100)
+        self.pump()
+        self._controller_ctx_mgr.__aexit__.assert_awaited()
+        self.get_success(do_update_d)