How to use a feature file without touching shaswat

I want to create a complete login feature file and write its unit tests.
And I could run that unit tests, whenever I want.
After, I want to create another feature file (let's call it filling a form) and write its unit test.

But in my case, only logged-in users can fill out that form.
So I want to use the login feature file inside the filling form feature file.
Of course, both feature files must be complete and separate from each other, and I could run them simultaneously.