Register a test which will be run when deno test is used on the command line and the containing module looks like a test module.

fn receive denops instance which communicate with a real Vim/Neovim.

To use this function, developer must provides the following environment variables:

DENOPS_PATH A path to denops.vim for adding to Vim's runtimepath

DENOPS_TEST_VIM An executable of Vim

DENOPS_TEST_NVIM An executable of Neovim

Otherwise tests using this static method will be ignored.