I'm the new hire on a codebase I didn't write

A new engineer at Mergify developed a daily quiz system based on real test assertions to familiarize himself with a codebase largely written by AI, where he initially scored three out of ten. This tool, built as a Claude Code skill, helps bridge the gap in understanding by presenting one question a day derived from the test suite, ensuring that each question traces back to a real assertion in the codebase, thereby avoiding the pitfalls of AI-generated inaccuracies. The quiz adapts dynamically as the test suite evolves and uses spaced repetition to prioritize areas of weakness, helping the engineer build a mental model of the system through interaction rather than passive review. The process is designed to fit into small breaks, allowing for continuous learning without overwhelming the engineer, though it currently lacks a difficulty gradient, treating common and rare scenarios equally. The approach is particularly beneficial for engineers whose roles focus more on reviewing than writing code, offering a deliberate learning method in environments dominated by AI-generated code.