Improved Guard Setup for Swift

In the last episode we showed how to run Swift tests automatically with guard, but it wasn't an ideal setup. We couldn't see compiler errors, nor could we see any output from our program using print. In this episode we leverage Ruby's open3 library to capture stdout and stderr so we can output it to the terminal in the appropriate colors.

This is a companion discussion topic for the original entry at https://nsscreencast.com/episodes/246-improved-guard-setup-for-swift