Your AI Should Be Writing Tests. The Unfair Advantage Every Vibe Coder Ignores.

A test is a note you leave for the computer. It says: "this thing works like this, and if it ever stops working like this, let me know." That's it. Imagine you built a calculator. You write a note that says "2 + 3 must equal 5." The computer checks this note every time something changes. If your calculator suddenly returns 6, the note fires. You don't need to understand how the calculator works internally. You just know it's broken because 2 + 3 is not 6. This is the entire concept. What a test looks like in practice Before any code, here's the plain-English version: I have a function called calculatePrice . I give it an item that costs $10 and a quantity of 3. I expect $30 back. If I get anything else, something is wrong. In Go, that becomes: func TestCalculatePrice ( t * testing . T ) { got := calculatePrice ( 10 , 3 ) if got != 30 { t . Errorf ( "expected 30, got %d" , got ) } } Seven lines. The machine runs this, checks the result, and tells you if it's wrong. You can have hundreds