A test going green is one of the most reassuring sounds in software. The CI bell rings, the checkmark turns, the PR merges. Everyone moves on.

But a green check only proves one thing: the code you asserted on did what you asserted. It says nothing about the thousand things you didn't think to assert on, and when an agent is writing the code and the tests, the set of things nobody thought about gets very large, very fast.

The screenshot problem

Most testing tools look at the surface. They render the page, take a picture, literally or figuratively, and compare it to what they expected. If the button is there and the text matches, the test passes.

The trouble is that an app is not its screenshot. A checkout page can render perfectly while the charge silently 500s. A success toast can appear while the order never reaches the database. The DOM says one thing; the program is doing another. A picture can't see the difference.

A false green is the most expensive kind of bug: nothing flags it. It ships, and you find out from a user.

What "proof" actually requires

To know an app works, you have to look at the app, not the picture of it, the network calls it made, the state it ended in, the errors it swallowed, the source line where the behavior diverged from intent. That's the difference between it looks done and it is done.

This is the layer most tools skip, because reaching it is hard. It means running inside the program, not beside it. It means asserting on behavior and state instead of pixels. It means a verdict you can trace to a line of code, not a diff you have to eyeball.

Trust, earned per run

When green means "the page rendered," you learn to distrust green, you click through the flows yourself, just in case. That instinct is correct, and it's also unsustainable once an agent is shipping all day.

The fix isn't more screenshots. It's a green that's earned: backed by the real signals the program emitted, reproducible on every run, and pointed at the exact place things broke when they break. A checkmark you don't have to second-guess.

That's the whole game, making the green mean what everyone already assumes it means.