Document controls together with their states

A screenshot captures only one moment of an interface. Implementing a reusable control also requires its states and transitions: keyboard focus, processing in progress and feedback after an error, for example.

Make behavior part of the component contract

• Give the control an unambiguous label and purpose.
• Describe keyboard operation and visible focus.
• Provide understandable loading and error feedback.
• Specify when an action is unavailable and how that is communicated.

Reusing a component helps only if these properties remain consistent. Additional link wrappers, different event handling or local style overrides can change its behavior. Test a representative use within the actual page as well.

The documentation gives design, development and quality assurance a shared reference. It makes the requirements for future variants explicit.