The list of browsers that pass the default EnhanceJS test suite includes modern browsers back to Internet Explorer 6, Safari 3, Firefox 1.5, and mobile safari (iPhone); while browsers like Internet Explorer 5.5, Safari 2, and the Blackberry browser will receive the basic experience. The EnhanceJS test suite can be configured to meet the needs of any project, so the division of browsers will change depending on the capabilities you choose to test. The test suite is also customizable, so you can run tests for any capabilities that are essential to the functionality of a given site.
EnhanceJS is developed and maintained by Filament Group, Inc. and was developed as part of the book “Designing With Progressive Enhancement“. It is available for download under MIT License; you can find further information & download on EnhanceJS Project Website.