Focus Order Testing
Focus order testing verifies that pressing Tab moves keyboard focus through interactive elements in a logical, predictable sequence — matching the visual reading order — rather than jumping around unpredictably, which is disorienting for keyboard-only and screen reader users alike.
Focus order usually follows DOM order by default, which is why it tends to break specifically when CSS is used to visually reposition elements without the underlying DOM order being updated to match — the page looks correctly laid out visually, but tabbing through it jumps illogically, since focus order follows the DOM, not the visual position.
Testing is straightforward in principle — navigate the entire page using only Tab and Shift+Tab, with no mouse at all, and confirm focus lands in the visually and logically sensible order — but it needs to be done on every meaningfully interactive page and re-checked whenever layout changes, since it regresses easily and silently.
