A browser test can be green and still be wrong.
It can pass because a mock returned an outdated response. It can fail because staging enabled a feature flag that no one documented. It can become flaky after a React upgrade even though the user-facing behavior looks unchanged. And when the same failure appears only in a minified build, the stack trace may be so unhelpful that the team blames the test before investigating the application.
These problems look unrelated, but they usually share one root cause: the test is running against a different system than the one the team thinks it is testing.
The difference may be configuration, data, rendering behavior, build output, infrastructure, or timing. Reliable browser testing therefore requires more than stable selectors. It requires evidence that the environment, application state, and execution path are what you expect.
Feature flags create multiple versions of the same application
