Post-launch bugs are costly for any application handling real user data, payments, or business-critical workflows, which is why QA is run as a dedicated pass separate from developer self-testing rather than folded into the development sprint itself. We use tools such as Selenium and Cypress for automated regression testing and Postman for API testing, layered with manual testing for the scenarios automation tends to miss.
This applies across every project type we deliver, but is treated as non-negotiable for anything touching payments, personal data, or workflows the business depends on daily.