I see your point but many editor (plugins) can enable switching between modules and their tests by using file name convention. Your code structure would need a specific (extra) config for the plugins which ‘just work’ for other Phoenix projects.
Also, have you looked at the Boundary lib? I know from experience that the use of path structures to ‘limit what can call what’ usually becomes problematic in larger projects. Boundary helps a lot to still keep things customisable but sane.
