Circle takes the pain out of automated testing, greatly increasing your developers' productivity.
Every time you push code to GitHub, Circle will automatically test your code, pushing working code immediately to Heroku/EC2/etc.
Circle does for testing what Heroku did for hosting. It is incredibly easy to use, fits into developers' workflow, and requires no maintenance. It is demonstrably fast, and so low friction that your entire team can be set up in one click.