Comment by mkramlich

except the code already works right (in proportional to your skill). and if it stops working right you did something bad. and you're using version control, so you can do diffs, rollback, do branches/forks, experiments, etc. This is a much faster workflow than being weighed down by automated test baggage. Again, some folks hold the code in their mind and do a very good job of making perfect incremental changes, only moving forward, no regressions. (not 100% of the time, but with experience/skill you can approach that, especially before you end your dev session for the day.)