At the last LondonR meeting Francine Bennett from Mastodon C shared some of her experience and findings from an analysis of a large prescriptions data set of the UK’s national health service (NHS). However, it was her last slide, which I found the most thought provoking. It asked for the definition of the following term: Test-driven analysis? Francine explained that test driven development (TDD) is a concept often used in software development for quality assurance and she wondered if a similar approach could be also used for data analysis.