rails-rspec error cannot load such file -- rspec/core/formatters/progress_formatter

Running bundle exec rspec solved it for me.

Running bundle clean --force did the trick for me, turns out there's some outdated gem in my system

I learned this from Victor Hazbun - expert on CodeMentor and Egghead.io:

Run gem list | grep rspec and pay attention to any gems that list multiple versions.

Then run gem uninstall ______ for each of those versions (removing ALL of the versions of each).

Then run bundle afterward. This will sync your versions with the versions in your gemfile.