Lago is an ad-hoc virtual framework which helps you build virtualizedenvironments on your server or laptop for various use cases. It creates andorchestrates virtual machines that can be used to run test suites and allow adeveloper to quickly test his code change on non-trivial flows such as livemigration even before starting the CI process. In this session, we will walkthrough the usage of Lago in the oVirt project and how it can be extended toassist virtualization developers. Virtualization software became a vital part of the IT infrastructure of mostcompanies nowadays. Making sure that the software works as expected in "realworld" tasks is hard, mainly because virtualization environments are usuallyhard to reproduce automatically. Lago is an ad-hoc virtual framework whichhelps you build virtualized datacenter on your server or laptop to run testsuites. Being a framework, it can be extended to implement any requiredworkflows needed by the tested software. We will discuss how Lago works with KVM and Libvirt to create a testenvironment, how it can be extended to help with automated system tests ofvirtualization products and how it is currently used by oVirt project to runautomated system tests and help developers testing their patches duringdevelopment phase. We will also review and compare Lago with tools likeVagrant, when applied to the virtualization development workflow.