Smoke test
A very quick check that the thing runs at all: it starts, the main page loads, the health endpoint answers. It says nothing about whether it is right, only whether it is on fire.
Agents can write a thousand lines and never start the program. A ten-second smoke test catches the embarrassing failure, and it is a sound first gate because it costs almost nothing.
Say it to your agent
“Add scripts/smoke.sh: start the server, wait up to 10 seconds for GET /health to return 200, load / and check the status is 200, then shut it down. Exit 1 if any of that fails. Run it before the full suite.”