Preview environment testing
what is preview environment testing?
Preview environment testing means running tests against a deployment built from a single pull request, rather than against a shared staging site. It tests exactly the change under review with nobody else's work mixed in. The cost is that somebody has to build and seed that environment, which is real infrastructure work with real recurring expense.
The advantage is isolation. On shared staging, two changes land together and a red run tells you something broke without telling you which pull request did it. A per-branch deployment removes the ambiguity entirely.
Some platforms hand you this for free. If your project already produces a deployment for every pull request, a test runner pointed at that URL gets branch isolation with no extra work.
Where it gets expensive is data. A preview deployment with an empty database cannot test checkout, so teams end up building a seeding endpoint, and that becomes a system with its own maintenance. Some testing vendors require this before you can run anything at all, which is a reasonable trade for a large team and a hard stop for one person with a staging URL.
in smolanalytics
The runner takes any URL that is reachable from where it runs, so a deploy preview, a shared staging site, or localhost through a tunnel all work the same way. Nothing here builds an environment for you and nothing requires one: that is the deliberate trade, and it is why the first run needs no account and no application installed on your repository.
How it works shows where this fits in the loop, and the docs have the exact behaviour.