Fixture library?

I’ve found several libraries meant for testing server code, essentially having RF act as a client.
I’m looking for a fixture framework that allows me to setup the surroundings for a system under test, no matter the type of connection - Not just the client(s), but also dependent services for that system.

My current challenge: The system accepts requests from a client, and as part of this processing the system issues requests to other systems. These systems are not available during tests so I would like RF to set up a Fixture for the system under test.

I’ve found the HttpCtrl and Rammbock libraries that seems to be able to do this partially, but is this it? Rammbock does not seem to be maintained and is still in “Alpha”…

Have I missed something - Does RF have this already?
Any experience that this is hard to make?
Anyone else missing such capability?