A Dropdown That Is Not a Div
Decide what you would build from the brief alone. Everything below it is available, but the exercise stops working if you open it first.
Build a filter dropdown: a trigger button, a popup list of options, single selection. It must work with a mouse, a keyboard and a screen reader.
Getting the roles and attributes right, verifying with an automated audit that reports zero violations, and shipping. Automated tools check the presence and validity of attributes; they cannot press Down. The dropdown announces itself perfectly and does nothing when a keyboard user tries to move through the options, Escape does not close it, and focus is left inside a popup that is no longer visible. The audit's green result is evidence about the markup, and it is routinely read as evidence about the component.