Install phabricator somewhere if you are allowed to. Use it to add comments/reviews to the code, for now for yourself but later maybe to share with the team. Create a branch to add your code changes toto, except for the tests that you are adding to the main branch.

Remeber, code is the embodiment of business rules. Often business are not aware of the rules until after thing work incorrectly. Non-beautiful odd can be the result of programmers dealing with the messy realities of trying to satisfy various stakeholders who are at odds with each other and can't articulate what they need.