[e_proxus]

I would recommend you learn the dbg module that comes with Erlang. Its a great tracing debugger able to trace existing code in runtime without having to modify the source. There are also several wrappers on top of the Erlang tracing tools, like Recon for example.

[wmock]

I'll need to do more research and maybe see if there are videos online showing how other developers debug in Elixir with those libraries.