Test API REST SCALA

I am developing an application with Scala, Akka and Spray and I want to test the services of the API.

I do not understand howspray-testkit helps us in testing. I also tried Specs2 and ScalaTest but neither of them are made to test APIs.

I just want a library that allow me to test API paths, adding headers, jsons to body and assert HTTP status and so son. What do you suggest me?

[EDIT]

I also tried Frisby.js and it is more simple. Maybe it is a better choice.

[EDIT -2]

I found Gatling. Does anyone know it??

Thanks!