Why does it take you twice as long to include unit tests? Here is one possibility: when you don't test it, you don't know it's broken, so you don't spend time

Why does it take you twice as long to include unit tests? Here is one possibility: when you don't test it, you don't know it's broken, so you don't spend time fixing it. When you do test, you do know it's broken, so you spend time fixing it. Hence, writing tests takes longer. Edit: But, if you only use 10% of your code, it is probably fine if 50% of it is broken.