Hi chikamsochinweubalilian, 

I’m afraid that, at Khan Academy, there are no full-length practice tests available; at the moment, we only offer articles, videos, and practice questions.

That said, I suggest you prepare for the Digital SAT using both Khan Academy's Official Digital SAT Prep for skill practice and College Board's Bluebook app for full-length practice tests. From College Board's Bluebook app, you'll be able to take full-length practice tests, and after each practice test, you can review your performance and read answer explanations for the questions you missed.

Hope this helps!