Fuel-Devops is a sublayer between application and target environment(all of supported by libvirt currently).
This application is used for testing purposes like grouping virtual machines to environments, booting KVM VM's locally from the ISO image and over the network via PXE, creating, snapshotting and resuming back the whole environment in single action, create virtual machines with multiple NICs, multiple hard drives and many other customizations with a few lines of code in system tests.
All documentation can be found here: https://docs.fuel-infra.org/fuel-dev/devops.html