Testing in Production

The practice of running tests, gathering feedback, and validating product behaviour in the live environment with real users, rather than relying solely on pre-release environments. In fast-moving teams, particularly startups, this is sometimes the only practical way to observe how a feature behaves under real-world conditions: real traffic, real data, real devices, and real user behaviour that a test environment can never fully replicate. It sits on a spectrum from deliberately staged experiments (feature flags, canary releases) to the more informal practice of shipping something and watching what happens. 

For example: rolling out a new onboarding flow to five percent of users before expanding it; or monitoring error rates and support tickets in the hours after a release as a form of post-deployment validation.