In this post, I demonstrate how to retrofit automated tests onto an untested legacy library. This is part two of a three-part series about how I resurrected ingredient-phrase-tagger, a library that uses machine learning to parse cooking ingredients (e.g., “2 cups milk”) into structured data. Read part one for the full context, but the short version is that I discovered an abandoned library and brought it back to life so that it could power my SaaS business: