diff --git a/deluge/config.py b/deluge/config.py
index 8671bc330..abf46d71b 100644
--- a/deluge/config.py
+++ b/deluge/config.py
@@ -144,11 +144,11 @@ class Config:
 
         self.load()
 
-    def callLater(self, period, func):  # noqa: N802 ignore camelCase
+    def callLater(self, period, func, *args, **kwargs):  # noqa: N802 ignore camelCase
         """Wrapper around reactor.callLater for test purpose."""
         from twisted.internet import reactor
 
-        return reactor.callLater(period, func)
+        return reactor.callLater(period, func, *args, **kwargs)
 
     def __contains__(self, item):
         return item in self.__config
diff --git a/deluge/conftest.py b/deluge/conftest.py
index ad7c8b30f..4266938fa 100644
--- a/deluge/conftest.py
+++ b/deluge/conftest.py
@@ -4,11 +4,13 @@
 # See LICENSE for more details.
 #
 
+import unittest.mock
 import warnings
 
 import pytest
 import pytest_twisted
-from twisted.internet.defer import maybeDeferred
+from twisted.internet import reactor
+from twisted.internet.defer import Deferred, maybeDeferred
 from twisted.internet.error import CannotListenError
 from twisted.python.failure import Failure
 
@@ -31,6 +33,29 @@ def listen_port(request):
     return DEFAULT_LISTEN_PORT
 
 
+@pytest.fixture
+def mock_callback():
+    """Returns a `Mock` object which can be registered as a callback to test against.
+
+    If callback was not called within `timeout` seconds, it will raise a TimeoutError.
+    The returned Mock instance will have a `deferred` attribute which will complete when the callback has been called.
+    """
+
+    def reset():
+        if mock.called:
+            original_reset_mock()
+        deferred = Deferred()
+        deferred.addTimeout(0.5, reactor)
+        mock.side_effect = lambda *args, **kw: deferred.callback((args, kw))
+        mock.deferred = deferred
+
+    mock = unittest.mock.Mock()
+    original_reset_mock = mock.reset_mock
+    mock.reset_mock = reset
+    mock.reset_mock()
+    return mock
+
+
 @pytest.fixture
 def config_dir(tmp_path):
     deluge.configmanager.set_config_dir(tmp_path)
diff --git a/deluge/tests/test_config.py b/deluge/tests/test_config.py
index 8bf470dbc..2840dbf5b 100644
--- a/deluge/tests/test_config.py
+++ b/deluge/tests/test_config.py
@@ -10,6 +10,7 @@ import os
 from codecs import getwriter
 
 import pytest
+import pytest_twisted
 from twisted.internet import task
 
 from deluge.common import JSON_FORMAT
@@ -83,6 +84,33 @@ class TestConfig:
 
         config._save_timer.cancel()
 
+    @pytest_twisted.ensureDeferred
+    async def test_on_changed_callback(self, mock_callback):
+        config = Config('test.conf', config_dir=self.config_dir)
+        config.register_change_callback(mock_callback)
+        config['foo'] = 1
+        assert config['foo'] == 1
+        await mock_callback.deferred
+        mock_callback.assert_called_once_with('foo', 1)
+
+    @pytest_twisted.ensureDeferred
+    async def test_key_function_callback(self, mock_callback):
+        config = Config(
+            'test.conf', defaults={'foo': 1, 'bar': 1}, config_dir=self.config_dir
+        )
+
+        assert config['foo'] == 1
+        config.register_set_function('foo', mock_callback)
+        await mock_callback.deferred
+        mock_callback.assert_called_once_with('foo', 1)
+
+        mock_callback.reset_mock()
+        config.register_set_function('bar', mock_callback, apply_now=False)
+        mock_callback.assert_not_called()
+        config['bar'] = 2
+        await mock_callback.deferred
+        mock_callback.assert_called_once_with('bar', 2)
+
     def test_get(self):
         config = Config('test.conf', config_dir=self.config_dir)
         config['foo'] = 1