Working in a codebase without tests is like taking a job at the top of a 4-story building that lacks an elevator. For me, the biggest benefit of TDD is to act

Working in a codebase without tests is like taking a job at the top of a 4-story building that lacks an elevator. For me, the biggest benefit of TDD is to act as increase my individual velocity. When I forget what my task is in the middle of executing it, running a test enables me to return to the task within seconds. So personally, I refuse to work professionally in a codebase if I cannot write (even hacky shell-script-based) tests. Also, tests enable me to better understand how someone else's code is supposed to be used.