They're often virtualized but don't underestimate mainframe persistence. At my last job as a consultant someone made https://github.com/manheim/antimony https:

They're often virtualized but don't underestimate mainframe persistence. At my last job as a consultant someone made https://github.com/manheim/antimony https://github.com/manheim/antimony for testing IBM TN5250 mainframe screens in Ruby - it's like Selenium but even more brittle. :>