The on-screen geometry contract

An acceptance contract for an interactive surface asserts where the interactive element sits relative to the region a person can actually see, not only that the element still exists and still holds focus. Continuity assertions describe the element; geometry assertions describe the encounter. No combination of continuity answers says where anything is, so a contract assembled entirely from them is fully satisfied by a layout that has put the focused element off the screen. This marks the limit of structural testing rather than an argument against it: a shape can be asserted precisely and still be the wrong shape, and choosing which property to make structural remains a judgement.