If you started in quality engineering decades ago, your whole mental model was forged in deterministic logic: assert(actual === expected). You took a business requirement specification, mapped out boundary values, wrote explicit test steps in TestRail or Jira, and automated them in Selenium, Cypress, or Playwright. In traditional QA testing, if an input of 2 + 2 yielded anything other than 4, you opened a severity-1 blocker, attached the stack trace, and kicked the build back to the developers.