You can review the main feature before we build every variation. We start with a small working version using representative examples, anonymized where needed. For a calculator, that includes empty fields, invalid values, and rounding. For search, we check what visitors see when nothing is found. We test behavior, rather than only checking whether a button responds when clicked.
We separate testing from production and agree on the checks required for acceptance. The frontend gets appropriate fields, useful error messages, and as few unnecessary scripts as possible. For content-rich sites, an Astro website can provide the foundation; features that need a server get a separate, suitable setup.