Ask HN: How do you handle “staging servers” in non-web environments?

Sorry if the title doesn't make sense, but I always work as a web developer and I wondered how do you handle testing / simulations / etc in non-web developments, especially in stuff like satellites, cars, etc.

How do you test your software? How, for example, is SpaceX software tested without launching a misile? I am sure you can test a lot with "fake" inputs but you can't be completely sure that it is going to be the same in the real scenario.

So if you want to share your insights from a not-common industry, use this thread!