Rails 4 integration tests for multiple Engines with Rspec + Factory Girl (shared factories)

Question

I'm using Codeship for continuous deployment. My app is setup so that the main app loads a few engines, and the engines isolate specific functionality. Each engine might have various rspec tests related to it's isolated functionality. Codeship spins up a copy of my app, runs a few commands, and deploys the code if everything works. Those few commands need to run all my tests. bundle exec rake or bundle exec rspec no longer work, as they only run the tests on my main container app (none of the engines).

I ended up created the following shell script that loops through the directories inside my gems directory, and calls bundle install and bundle exec rspec:

retval=0
for dir in gems/*/
do
    dir=${dir%*/}
    echo "## ${dir##*/} Tests"
    cd gems/${dir##*/}
    bundle install
    if ! bundle exec rspec spec/ --format documentation --fail-fast;
    then
        retval=1
        break
    fi
    cd ../../
done
exit $retval

This works well. All my tests are executed, and it exits with an error if any tests fail. In an effort to see if there was a better way to accomplish this, I tried moving this functionality into a rake tasks. I attempted a couple methods. I used the FileUtility methods to loop through the directories and the System method to call the same bundle install and bundlee exec rspec as above. The commands are called, but when it is ran from the rake tasks, their is a problem with the factories. If Engine A calls factories from Engine B, the returned values are nil. I'm calling shared factories this way (example from Engine A):

FactoryGirl.define do
  factory :Model, class: EngineB::Model do
  end
end

Sorry this is long winded. To sum up my questions:

1) Is the shell script a good way to manage tests? I haven't ran into any issues with it yet.

2) Do you know why calling that shell script from a rake task causes the factories to return nil values?

3) Do you know why mimicking the shell functionality in a rake tasks also results in the factories returning nil values? (probably same problem as above)

4) Is there a better way to share factories? I've placed all models that are referenced in multiple engines in one engine.