During the development of REPL.nvim I had to be able to test the plugin without relying on any particular REPL present on the development system. The solution was to create a mock REPL, a shell script which acts like a really dumb REPL. Here is the code:
Integrating a REPL in Vim has been a difficult issue in the past, but with Nvim's built-in terminal emulator it is just a few commands away. My new REPL.nvim plugin now puts the REPL only one command away, for any programming language you wish. The end goal is to have a complete generic and configurable REPL framework which can be customised to the needs of any language and which forms a solid foundation for other plugins as well.