We have two web apps that share the same database and models. To keep it DRY we created an engine that contains all those models. This engine is included in the respective a
Ok so this works: https://github.com/thoughtbot/factory_girl_rails/pull/42
As it says on that pull request, include that code snippet in your core engine.
In the core engine you also need to modify your ".gemspec" file to add in the "spec/factories" files:
s.files = Dir["{app,config,db,lib}/**/*", "spec/factories/**/*", "LICENSE", "Rakefile", "README.md"]
Then those factories will be available in the application that includes your engine.