Devloop is an automated Rspec runner for Rails apps inspired by TLDR and Rust (full story). The purpose of this tool is to provide continuous and instant feedback when working on the Rails app. It runs only specs from lines modified in the recent git commits. Even if you have a large spec/user_spec.rb file, you'll receive specs feedback in ~second on each file save.

Optionally, you can edit first line of any spec file (i.e. add #) to run all the tests from it.

In your Gemfile:

gem "devloop", group: :development

Now you can run:

bundle exec devloop

You can also use it without adding to the Gemfile:

gem install devloop
devloop

Remember to run the devloop command from the root of your Rails application.

While devloop process is running it will automatically execute tests related to the recently modified lines of code from spec/ folder.

Devloop will automatically detect if Spring is enabled for your Rails app. I've observed it reduces time needed to run specs by ~4x.

If currently there are no modified spec files, devloop will run tests based on changes in the most recent git commit.

This is in a very early stage of development so feedback is welcome.