What is the way to write tests against a 3rd party software like redis

I'm not sure if this is the right forum to ask this question if not kindly point me in the right direction.

I wanted to create a library/client for a 3rd party tool, which is similar to redis. And for the unit/integration tests, I see that in predis library, they have tests which directly interacts with a running redis instance and there are tests which make use of mocks.

So my question is that, is it okay if I write tests running against an actual instance of the 3rd party tool or should I employ mocks all the way?