In order to run all test functions in a test page, JsUnit naturally needs to know what those test functions are. It’s able to get a list of those functions from Firefox, Safari and Opera, but it’s not able to get them from Internet Explorer. So in IE, JsUnit has to resort to searching the text of all scripts for strings that look like test function names. Unfortunately, it doesn’t understand comments so commented-out test functions will end up running anyway.