Using the guard gem to run tests etc in your Rails app normally requires some form of file system monitoring.
The monitoring will be OS dependant and rb-fsevent is the gem for OSX. This can be added to the Gemfile conditionally with:
gem 'rb-fsevent', :require => false if RUBY_PLATFORM =~ /darwin/i
Unfortunately when you next push to Heroku you are likely to get an error along the lines of:
This is due to Heroku not allowing conditions in the Gemfile, even in the dev group.
The alternative is to put the gem in it’s own group:
And on non Mac systems run
bundle install --without darwin (this only needs to be run once, the without setting is remembered for future bundle installs). Then for Heroku run
heroku config:add BUNDLE_WITHOUT="development test darwin"
Don’t forget to add –remote remote_name if you are pushing to a remote other than heroku (e.g.
heroku config:add BUNDLE_WITHOUT="development test darwin" --remote staging) and don’t forget to merge your amended Gemfile into master before running
git push heroku master.