My question is, how should my Erlang app reliably find a binary in the priv directory, not just in production; when installed properly, but during common test?
I realised today when I added a travis-ci configuration to an old Erlang app and pushed it to git-hub, that the process by which it works locally for me, is a little more fragile than I thought. The travis-ci build failed because it, not unreasonably, checked out my repo into a directory named after the repo, which is of the form erlang-APP. Locally my app is in a directory called APP-VSN though.
The result of this is that a call to code:lib_dir(APP) returns a correct result during the common test run locally, but if I rename my current directory to erlang-APP instead of APP-VSN (or just APP works too) my local build fails, just like it does for travis-ci, because code:lib_dir(APP) returns {error,bad_name}. The behaviour as though .. is added to the library path for rebar ct.
Renaming my github repo from erlang-APP to APP resolves the travis-ci build failure... but knowing the build tests only pass depending on the name of the directory the repo is checked out into doesn't sit right with me.
One way could be to use a soft link (either in the repo under version control, or created when initializing the tests), and make your Erlang code path go via the link. E.g., "./APP" -> ".", or "./lib/APP" -> "..".