That's quite impressive by the standards I'm used to. Do you mind if I ask what scale you're operating at and what tools you use to manage the staged rollout?
Our scale isn't ginormous. Fewer than two dozen microservices and we sometimes fudge the 'microservice' definition somewhat to allow some of those services (such as pure lookups) to host their isolated tables in the same database schemas/instances. We always mock external web service calls in the test env since a Fedora update either will or will not screw up the ability to hit an endpoint via HTTP (has never happened) -- in other words, hitting a real, live service would add nothing to the results of the dev test outcomes.