Testing for deployment
It's quite embarrassing to send a compiled and nicely working program to a customer only to get a response back that it won't even start because a required library was not found or it can't access a database file it was expecting. In your development environment, you have everything set up to work with files, packages, and databases in expected paths, firewall ports you opened and forgot about, and configurations primed for optimal use. But a customer is unlikely to have any of this in place. Even when you're just giving a customer an update, at some point that customer may need to get a new computer or upgrade their phone and need to reinstall your software—and possibly restore a database backup.
One of the best ways I've found to test for these cases on Windows is to use virtual machines.
Using virtual machines
With a virtual machine, you get a completely separate and customizable platform with an operating system...