How do I handle api testing in a backend project?

I've just learned the basics of express/backend and am attempting to make a backend playground for myself. I'm using an Angular-cli project for my front end and I was wondering how I should handle testing the api calls.

I know I can write karma test in the the front-end project to make http request for testing, although I feel like it seems contradictory to have the backend workflow also require the front-end and mess with their project. My mindset is that we do this to keep their workflow separate although I'm looking for a second opinion to be sure about this.

Can anyone confirm if working on the client side project is the way I should be doing my test or if it really should be handled in the backend project. What is the proper way to test backend api and what resources should I use?