Earlier quoted context omitted.
Test it in production.
... which is a terrible idea
Testing in production (with rollbacks and safeguards) is actually how things are done in many endeavors in life, especially with processes that are reversible or where the cost of mistakes are bounded. Reality is a better teacher than a simulation. This it not to put down tests -- it has its place -- but in complex systems, it's impossible to have comprehensive coverage. Stochastic things show up in real life that never show up in tests.
In software, you just keep building up your test suite. In complex stochastic systems, you'll have a much harder time building tests.
Software people have a notion that the world should be TDD-driven, but it doesn't really work like that.