Code review comment for lp:~unity-2d-team/unity-2d/testability-integration

Why Xdo?
- Best Ruby library I can find to control X. Emulates mouse & keyboard inputs, has basic clipboard support, and excellent abilities to control the window manager.
- Makes use of existing X test-applications (xdotool, xsel..)
- Easily extendible to support host & system-under-test separation (using @sut.execute_shell_command). Right now, it is required that we test on the host machine.

Why a copy in the tree?
- Rubygems are developer packages, we cannot depend on their stability
- As above, want to modify the library for our own needs. Good to push any fixes to original project however.