We write an RSpec-style test runner from scratch. During this screencast series, we'll continually build on this runner to see how to write good tests, and do demystify testing tools' internals. (Note 1: The test runner is similar to the one built in "Building RSpec From Scratch" seven years earlier. Note 2: ANSI escape codes are mentioned briefly here. There's a bit more about them in "Text Editor From Scratch".)