Update

It seems you could do this already with :AV. I’ll leave this post here for posterity’s sake.

Using vim for Rails development I often found myself entering

:Rcont :vsp :A

to see my controller spec on the left, with my controller on the right. now with this in my .vimrc:

nmap vspa :vsp<cr>:A<cr>
nmap RC :only<cr> :Rcontroller<cr> :vsp<cr> :A<cr>
nmap RM :only<cr> :Rmodel<cr> :vsp<cr> :A<cr>

I can do it all at once with just the following in normal mode
Rspec and Controller:

RC

Rspec and Model:

RM

vertically split, and then open the associated file:

vspa