MediaWiki-Vagrant is a portable MediaWiki development environment. It consists of a set of configuration scripts for Vagrant and VirtualBox that automate the creation of a virtual machine that runs MediaWiki. The virtual machine that MediaWiki-Vagrant creates makes it easy to learn about, modify, and improve MediaWiki's code: useful debugging information is displayed by default, and various developer tools are set up specifically for inspecting and interacting with MediaWiki code, including a powerful debugger and an interactive interpreter. Best of all, because the configuration is automated and contained in a virtual environment, mistakes are easy to undo.