Run the commands from your project's root directory:
# run all specs in the project's spec folder
bundle exec rspec
# run specs nested under a directory, like controllers
bundle exec rspec spec/controllers
# run a single test file
bundle exec rspec spec/controllers/groups_controller_spec.rb
# run a test or subset of tests within a file
# e.g., if the 'it', 'describe', or 'context' block you wish to test
# starts at line 45, run:
bundle exec rspec spec/controllers/groups_controller_spec.rb:45