How would you test a pen (or a lift / elevator)?

The interviewer is not interested in pens. They want to see how you think. So start with questions, then work through categories.

1. Clarify requirements. Who is it for (kids, office, astronauts)? Ballpoint or fountain? What surfaces should it write on? Any price or lifetime targets?

2. Then structure the tests (example: a lift):

• Functional: pressing a floor button takes you to that floor; doors open and close; the display shows the correct floor; up/down call buttons on each floor work; emergency button and phone connect to help.
• Usability: buttons reachable from a wheelchair, Braille on buttons, audio floor announcements, clear labels.
• Performance: time to arrive after a call; behavior at rush hour with calls from many floors; maximum load.
• Safety: overload alarm and refusal to move; doors reopen when something blocks them; behavior during a power cut or fire alarm; it never moves with doors open.
• Edge and negative cases: pressing all buttons at once; pressing the current floor; pressing a button many times; pressing “close door” while someone enters.
• Compatibility / environment: works in heat, cold and humidity.

For a pen, the same structure applies: does it write (functional), is it comfortable (usability), how many pages until the ink runs out (performance), is the cap safe if swallowed by a child (safety), does it write upside down or on wet paper (edge cases).

Finish by saying how you would prioritize: safety first, then core functions.

Learn more: Types of Testing