I agree. It's impressive to me the people who are claiming that something like unit testing can compare to these kinds of tools, without seeing the general dire

I agree. It's impressive to me the people who are claiming that something like unit testing can compare to these kinds of tools, without seeing the general direction these tools are headed in. Unit tests are helpful, no doubt. But compare the following: - Spend several minutes writing a small test suite for the functionality you're writing. Write that functionality until you think it's correct. Compile, run. See a "Pass!" or "Fail! (reasons: ...)" in your console or IDE, fix it until it's working. Feedback loop is measured in minutes, seconds at best. Vs.: - Write the functionality. As you're writing, you see the data flow through your program in real-time, immediately identifying bugs. Any unit tests you may have are _even more useful_ because you can inspect your program at any level, without having to debug or step through your program. No need to re-compile and re-run, no need to even Alt-Tab. Feedback loop is measured in milliseconds. Light table isn't quite there yet, but it's a strong step in the right direction. Unit tests help, but they don't obviate the need for better tools. To give a bit of context on the direction these tools are trying to move in, Light Table was heavily inspired by the work of Bret Victor, who bases his work on the idea that, quote, "Creators need immediate feedback to what they're creating." If you haven't seen his _Inventing on Principle_ talk [0], you should. It's one of the most eye-opening talks on software and design I've ever seen. [0] http://vimeo.com/36579366 http://vimeo.com/36579366