2 routers on one switch

Hi guys need some help.

I currently have one router(MS TMG) and one switch(some old unmanaged switch) with one subnet(192.168.2.0/24). Now I have to replace the old router with new one. Configuring the new device will take some time and I want to test everything properly so I connected the new router to the switch and use new subnet(192.168.1.0/24). This works fine but devices from different subnets dont see each other. The question is can I just create new static route on both routers pointing to the other subnet/gateway, or is there something else i need to do?

Thanks