How to test a Symfony application that depends of an API

I have two Symfony projects (a back application and an API).

The back application is the graphic side, it just call API.

The API is connected to database.

I would like to test my back : currently, at each test, I make an API call to reload the database but I have the impression that I make it wrong.... and moreover it's so slow...

There is a better solution ?

Thanks