Pytest asserting from another function's callback

I am using pytest to test an airplane state transition. I am testing the landing() function that is predefined and calling it from another function. It looks something like this:

def landing():
    airplane_actions.decrease_altitude(ft=10000)
    time.sleep(30)
    airplane_actions.decrease_altitude(ft=5000)
    time.sleep(30)
    airplane_actions.decrease_altitude(ft=0)

In my testing module, test_plane_actions.py, I am calling this landing() function, however, I want to be able to assert the altitude values before each sleep.

test_plane_actions.py

def test_plane_actions():
    # Do some setups
    # assert
    plane_actions.landing() # I want to assert the altitudes in here from this function.

Is there a way to have the landing() function callback the test_plane_actions.py module during each sleep period and make an assert during each sleep period? Or perhaps a delayed assert? Let's assume we cannot decompose the landing() function and I want to be able to just call it in the test_plane_actions.py.