Comment by leommoore

I think it depends on the nature of your application. In my experience, in a startup situation the product design can be iterating quickly so both the tests and the code itself can be out of date very quickly. Personally would wait until I was close to product/market fit before writing tests.

Obviously, if you have a clear understanding of the finished product like in many enterprise applications then testing makes sense.

I would however, strongly recommend it if you are doing nuclear reactor software ;-)