This story is a sequel to The Iron Horse: Everything's Better With Robots!
Turing Test is a robot pony built by a formerly evil "mad scientist." It's the day before Sire's Day, and she's spending time with Twilight Sparkle, her very best friend and mentor. But she has questions: Why should Starlight Glimmer go free while her father is behind bars? And what separates one former villain from another?
(Set in early Season 6. A meditation on justice, on family, and on what makes a suitable pie filling.)