Analyst: “So this part of the UML diagram is right? A fizz always belongs to a buzz?”

Domain expert: “Yes, always”

Analyst: “Any exceptions you can think of?”

Domain expert: “No, none at all.”

—-

Forward to day 1 after “delivery” of the implemented system.

Domain expert is now using the system for the first time in a real-life situation:

“It doesn’t let me save the fizz I’m creating. How does this handle a case where a fizz doesn’t yet belong to a buzz?”

> “It doesn’t let me save the fizz I’m creating. How does this handle a case where a fizz doesn’t yet belong to a buzz?”

You are not describing a scenario that involves diagrams of any kind. You are describing a scenario where an analyst missed critical requirements and failed to accommodate them in a design. Blaming UML for a design mishap is like blaming your notepad for you failing to buy some groceries.

Is there an equivalent of The Mom Test for talking to domain experts?