expose jsdom instance for config in tests

[zcrumbo]

This popped up while trying to write tests that involved sessionStorage - there's no way to do things like change jsdom's window.location.href without having access to the jsdom instance itself.
Can we expose a reference to it as a global in setup script?

[peripateticus]

Definitely. One workaround that I've used is that you can set window properties via global.window that is set up via jsdom-global. I recently helped someone with this who was trying to write some tests around window.WebSocket.