test(react-router): check the route context at beforeLoad, loader…

…, and `component` (#1708)

* test(react-router): initial tests for checking the route context

* chore: some comments so I know where I'm at

* test(react-router): make sure that context modification works

* chore: remove the element ids to simplify things

* chore: use simple naming for this stuff

* test(react-router): making sur the mock fn is only called once