4. Testing software means more than just putting code into production and seeing what happens
Regression and stress testing separate the pros from the amateurs. They always have, and they still do. Regression testing makes sure new stuff doesn’t break old stuff. Stress testing makes sure everything will perform well enough when everyone starts banging away at it.
IT, being professional, maintained at least three environments -- development, test, and production. That meant buying three of everything. And maintaining them, too. Ouch!
Now, even when you maintain your own data center, spinning up a test environment in the cloud often makes more sense because you only have to pay for it while you need it. Depending on your production environment it can work quite well for regression testing, too.
Stress testing? Not yet. Too many variables, at least for the time being.