Run IHM tests with webservice assertions in Codeception

I would like to run IHM tests, verify some values comming from a webservice in the testing framework Codeception.

I don't want to test the webservice, I need it to verify that values which are displayed on the screen are correct.

My question is: How can I do to do assertions without testing the webservice, to compare what is displayed to what is in database ?

Do I have to use several actors ? how many yml files do I need ?

Any answer will be appreciated

Dim