Writing tests. I got along years professionally without, employers weren't enforcing it. Over the years I think it made my code better structures, easier work/h

Writing tests. I got along years professionally without, employers weren't enforcing it. Over the years I think it made my code better structures, easier work/handover with other engineers, less feat to restructure code and ultimately it saved me from many small and big bugs. It doesn't have to be full coverage, or writing tests before code, any tests are better than none.