I have been working on a .NET assertion library called Axiom Assertions. It started as a way to learn how assertion libraries work, then grew into an experiment around deterministic output, batching, analyzers, and AI-focused test assertions. The repo is here: https://github.com/spearzy/Axiom-Assertions This did not start as a plan to overthrow every assertion library in .NET. That would be a bit much. The ecosystem already has good tools, and most teams quite reasonably do not wake up looking for a new way to write Should() . The real reason was simpler: I wanted to understand how assertion libraries work by writing one myself. At some point, reading the docs for existing libraries only gets you so far. You can use an assertion library for years and still not really think about how much work is hiding behind a nice failure message.…