Automation test cases generation

I wanted to generate testcases of my php source code.
In my code structure i have src folder inside which i have controllers folder and models folder . there are approx 25 classes in each folder .
I have created a tests folder parallel to src folder inside which i have written testcalsses of 3 classes of controller folder .
I wanted to generate testclasses for all other controller files for public function using GPT .
My concern is that i am not able to upload more than 20 files in Assistant so GPT has no context of all the files .
How can i achieve this ? please guide …
Also is there any in GPT through which i can give repo access and it can automatically fetch the code from gitlab.