I'd be really interested to know what other organisations do as far as testing changes or processes prior to deployment in their on-prem production environments. Because of our dependence on multiple physical gateways, we have never been able to get the resources to duplicate the Prod environment. Over the weekend, we had two issues, one when testing a DR pool failover and another with updating certificates. Both were disruptive and now that we need to investigate them it is almost impossible to do so, without a duplicate environment, without impacting our users.
For tests to be valid, the 'lab' needs to duplicate Prod as closely as possible. Whilst our servers are virtual, having twice as many is not a scenario I am looking forward to.