[LiKao]

> But why risk it?

Because testing environments often still mock some parts of the system and there may be subtle differences between mocked systems and live systems.

When I worked at a company that send out SMS to cell phones, we first tested our system without any connection to the network with our simulated SMS service provider. When we tried to go live, we tested a few live SMS on actual phones we controlled. It turned out, that there were some subtle differences between our mock SMS service and the real service, so we had to stop deployment and first fix the issues.

That was after months of testing in the test environment without any sign of the bug before we tried to go live.