rnvimr VS lf

You can ranger inside of Neovim with this plugin rnvimr. Check it out. Neo-tree is another plugin that I like as a file manager. And also mini.files is another option if you prefer a more minimal approach and the ability to manipulate files like you edit a normal Neovim buffer. I'm pretty sure there are other great options out there as well, these are just my personal preferences.

https://github.com/kevinhwang91/rnvimr is pretty good, it opens ranger in a floating terminal and takes care of file renaming and deletion, etc.

Ranger inside Neovim for when I need it

This plugin is unique from the other alternatives such as ranger.vim and rnvimr in that my plugin has no dependencies besides ‘ranger’ and written in 100% lua.

chadtree for dealing with files in the current project & Rnvimr (which basically integrates Ranger) when I want to work with files all over the disk.

Although Ranger is a terminal application, you can use it in neovim via some plugins like rnvimr.

If you don't mind switch to another plugin I highly recommend rnvimr to use ranger, a real-world, feature-complete file amanger perfecrly integrated in nvim.

Also, considering your code, I am not sure, bit I think it is a terrible idea to install libraries on other people computers without clearly stating it, or perhaps stating it as a requirement and what is going to happen. I am referring to your "test suite". Especially since you are actually using ERT which is included in Emacs. Why should you fetch org, undercover or Quelpa??!! or even require it for your tests is an even bigger mystery, not to mention other libraries. You should probably redesign your tests completely. I haven't looked much at rest of your code in tests, or your main code, I just saw the first lines of tests.el.