Please let me clarify why we don't support framesets. The
frameset features are marked as obsolete in the W3C Recommendation. As TestCafe is based on HTML5 standards that do not support frameset, TestCafe does not support frameset either. So, we'd like to focus on up-to-date features that will give best the experience in testing modern web applications. Nevertheless, we will keep in mind this feature and possibly will find a way to support it in the future.
Therefore, we'll be happy if TestCafe fits your need for your other projects and we are always ready to help.