Easy python file <--> python test file switching if your python test files live in a tests folder alongside the implementation files and the naming is similar (something.py <-> tests/test_something.py).
Add your preferred binding to your vim config like this (this one does for <leader> .):
autocmd FileType python nnoremap <silent> <leader>. <Esc>:call OpenPythonAlternate()<CR>
Inspiration
Based on vim-open-alternate, which does not have python and is unsupported and is based on Gary Bernhardt's dotfiles.