If you've ever tried to run a large Playwright test suite in parallel — the kind that tests email verification flows, magic links, or password resets — you've probably hit this problem:
Two tests run at the same time. Both sign up with the same test email address. Test A waits for a verification email. Test B's email arrives first. Test A reads it. Test B times out. The whole suite goes red, and you spend an hour debugging a race condition that only happens in CI.
This is the inbox collision problem. It's subtle, it's intermittent, and it's completely avoidable.
Why shared inboxes fail in parallel CI
Most email testing tools give you one of two options:
