rest api – Is there any way to log in to the frontend without going through the log in page?

I am trying to implement some UI tests written in selenium.
There are a number of test cases which rely on the user being logged in. If I use the frontend login form to log in, and one day I find the login page is broken, then all other tests that depend on the user being logged in will fail and nothing can be said about whether that functionality actually works or not.

So I would like to find a way to bypass the login form.
I have managed to call the API at /rest/V1/integration/customer/token. This returns a PHPSESSID cookie and a token, however my understanding is that this only authenticates to the REST APIs and does not allow me to log in with a browser – and after setting the cookie I am still logged out.

Is there any way that I can log in (without changing any Magento code) without using the login form?