Local library with dub

[JG]

Hi

I want to put some code together in a local library that is then 
used by several other projects. I am running into a few problems. 
Firstly when I try and configure the code to be a library (dub 
init, add d files to source, and remove source/app.d - perhaps 
this wrong) dub test no longer seems to work?

Secondly I am having problems getting dub to add the library code 
to other projects. It seems to work if I run dub add-local 
path/to/library and then add the appropriate dependencies to the 
projects dub.json file. However, I didn't manage to find 
documentation that explains exactly how this should work. Also 
there seems to be some mention getting this to work with versions 
(in the documentation about dub add-path), which I couldn't 
follow.

Does anyone know in more detail how this works or how I can find 
out?