How to unit test code that runs celery tasks?

The app I am working on is heavily asynchronous. The web application runs a lot of tasks through celery depending on user actions. The celery tasks themselves are capable of launching further tasks.

Code such as the one shown below occurs in our code base quite frequently.

def do_sth():
    logic();
    if condition:
         function1.apply_async(*args)
    else:
         function2.apply_asynch(*args)

Now we want to start unit testing any new code that we write and we are not sure how to do this. What we would like to assert in our pytest unit tests is that we want to see if function1 actually got called. We do not want to necessarily run function1 itself as we will have a unit test for the function1.

I do not want to be running celery as a process, neither do I want to run any AMQP broker during the unit test session.

Is this achievable?