In the previous chapter, we covered tests as a must-have prerequisite for automated deployment. Now, let's take a closer look at the other part: deployment and reproducibility of the production environment.
Modern virtualization technologies allow us to create cheap virtual machines; this is essentially an emulated computer running on a real computer, with an operating system, I/O, and everything else. From the viewpoint of a program that runs inside a VM, it is almost indistinguishable from the real computer, at least if the program does not touch low-level interfaces, which is highly unlikely if you do regular web development.
Since everything on a virtual machine is controlled by the host, memory, ...
