If it is as you say, then why upgrade ever? How would we even discover bugs in software until it is used?
To have progress we need to change things. When we change things, we may break things, regardless of tests.
To quote deijkstra: "testing can be a very effective way of showing the presence of bugs, but it is hopelessly inadequate to show their absence". From 'the humble programmer'.
Production is the only way to eventually discover the stability of any software, even with 100% test coverage. It's a necessary evil in the support of progress.
To have progress we need to change things. When we change things, we may break things, regardless of tests.
To quote deijkstra: "testing can be a very effective way of showing the presence of bugs, but it is hopelessly inadequate to show their absence". From 'the humble programmer'.
Production is the only way to eventually discover the stability of any software, even with 100% test coverage. It's a necessary evil in the support of progress.