Start with writing Unit tests for basic functionality. Do not do the cardinal sin of writing unit test for every goddamn function in the codebase like a rookie

Start with writing Unit tests for basic functionality. Do not do the cardinal sin of writing unit test for every goddamn function in the codebase like a rookie. Start fixing code, one by one only if it can be tested by Unit tests. Remember you need to first learn the code base and context because harping "complete mess". Maybe they did not have time, maybe timelines were more imp. That is what industry is about especially when you do not have enough Engineers. Plus this new wave of PMs who want features at any cost, doesn't make things any easy. Good luck