Sugar is test driven from its inception, and has an extensive suite of unit tests. Below you can run the tests against the production version in your browser.
Some of these tests can occasionally appear to fail. There are various reasons for this. Date tests can fail as they are exact to the millisecond, and a slight CPU hiccup can throw them off. Finally, the Object.watch method is not compatible in IE8 and below, and is the only method that isn't fully compatible.