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Short answer
Use variables, mathematical expressions, and conditionals to simulate real app behavior such as shopping carts, calculations, and sign-in without writing actual code.
Explanation
Traditional prototypes required creating 20 duplicate screens to simulate adding an item to a cart, changing its quantity, and calculating the total. Modern advanced prototypes use a numeric variable (CartCount) that changes when the (+) or (-) button is tapped, with conditions such as "If CartCount == 0, show EmptyState." This improves usability testing and lets users freely test their own inputs.
Common mistakes
- Over-engineering complex prototypes for weeks instead of producing a real proof-of-concept in code.
- Relying only on direct screen links for tests that depend on calculations and data interactions.