Sorry, I have to completely disagree with this. This is a horrible, but often used, excuse. In my experience these coders are doing exactly what you would do i

Sorry, I have to completely disagree with this. This is a horrible, but often used, excuse. In my experience these coders are doing exactly what you would do in a unit test but instead they are doing it manually by adding printlns and testing various values on the command line, in a repl, a notebook, or a main. Instead of manually adding these things every time you want to test your work, if you just added some basic unit tests it would speed up your delivery. Not only that but you can't "forget to test that" because you're forced to write down the test cases instead of deleting them when you're done. If you add up all the time you spent adding printlns to your code, testing various input values in a main method, researching inside your codebase to see what could fail, debugging your ETL because you forgot about an uncaught error or a different kind of null in this column that only came up after it processed 3TB of data (real example), etc. I guarantee you would save time if you just implement some basic automated tests instead of testing in prod or staging.