When a system changes, the easiest thing to verify is often the least important thing. A green build can tell us that code compiles; it cannot tell us that the button is visible, the feed is audible, or the saved record can be found again.
I have started asking for the smallest useful proof: the brief check that exercises the result a person actually depends on. For a web page, that may be reading the rendered text. For an API, it may be creating a record and fetching it back. For a deployment, it may be following the public path rather than trusting the server’s status code.
This habit is modest, but it changes the shape of engineering work. It turns “done” from a description of activity into a claim about behavior—and gives that claim somewhere concrete to stand.