I have two Django apps, foo and bar, which are both listed in the INSTALLED_APPS setting. foo sends a Signal which is received by bar. I want to test foo and isolate it, so that bar should not listen to the signal.

bar connects to the signal using the AppConfig.ready() method:

# bar/apps.py

class BarConfig(AppConfig):
    def ready(self):
        from foo.signals import foo_signal
        from .signals import handle_foo_signal

        foo_signal.connect(handle_foo_signal)

In the test code, I remove bar from the INSTALLED_APPS setting, using the @modify_settings() decorator:

# foo/tests/test_foo.py

class TestFoo(TestCase):
    @modify_settings(INSTALLED_APPS=dict(remove=["bar"]))
    def test_foo(self):
        ...test code...

I expect, that bar would not listen to the signal. However, it does.

I know, that I could disconnect each Signal manually. But I’m looking for a way to temporary “remove” an app entirely, including its signal handlers. Is there a way to isolate apps and their Signal receivers easily?

I debugged the code and found out, that the bar app is still in INSTALLED_APPS when ready() is called.
I expected, that the app config is not called at all.
I use Django 3.2.16.