Would a software tester really test a lift?

Not its safety certification: that is done by the installer and authorised inspectors under local rules. The question checks whether you can find behaviours, boundaries and failure cases for any system. Say that early, then answer as if you were testing the lift controller's behaviour.

Should the lift stop at floors in the order the buttons were pressed?

Usually not. Most passenger lifts serve calls in the direction of travel (collective control), so pressing 8, 2 and 5 going up gives stops at 2, 5 and 8. Ask which control logic the lift uses rather than assuming.

Test cases for a lift (elevator)

Assumes a passenger lift in a ground-plus-ten building (floors G to 10, plus one basement for parking), with car buttons, up and down landing buttons, door open and close buttons, an alarm button, an overload sensor and an access-card reader for the basement and floor 10.

How to answer in an interview

Ask before listing: how many floors and lifts, the rated load (from the plate inside the car), whether lifts work as a group, which floors are restricted, and what must happen on a power cut or fire alarm. Say that safety certification is done by authorised inspectors, and that your cases cover the controller's behaviour. Then group: calls and travel, doors, load, emergencies, access, accessibility and performance.

Scope and test data

Physical safety checks (brakes, ropes, landing door locks) are for qualified lift technicians; where a case below touches them, it is written as "observed during the technician's inspection". Use a soft foam block, not a hand, for door obstruction tests, and test weights for load tests. Waiting-time and levelling limits must come from the installer's specification before these cases can pass or fail. These are designed cases, not an execution report.

Calls and travel

ID	Category	Test case	Expected result
E01	Functional	Lift idle at G; press Up on floor 3	Lift travels to 3, Up arrow lights, doors open
E02	Functional	Inside the car, press 7	Lift travels to 7, stops level, doors open, display shows 7
E03	Functional	Press the button for the floor the lift is already on	Doors open (or stay open); no travel
E04	Functional	From G going up, press 8, then 2, then 5	Stops at 2, 5 and 8 in that order (direction order), unless the spec says otherwise
E05	Functional	On floor 4, press Up and Down while the lift passes going up	Lift stops for Up on the way up; the Down call is served on the way back
E06	Boundary	Look at the landing panels on floor 10 and in the basement	Floor 10 has no Up button; the basement has no Down button
E07	Boundary	Travel to the top floor and to the basement	Lift stops level at both ends and never overruns
E08	Negative	Press B (basement) without showing an access card	Call is not registered, or the panel asks for a card
E09	Functional	Press a car button twice to cancel it, if the lift supports cancelling	Call is cancelled and the light goes off; if unsupported, nothing changes
E10	Functional	Leave the lift with no calls for the idle period	Parks at its home floor if configured; doors closed; car fan and light switch off as specified

Doors

ID	Category	Test case	Expected result
E11	Functional	Press Door Open while the doors are closing	Doors reopen
E12	Functional	Press Door Close after the doors open	Doors close sooner, or the button is ignored, as specified
E13	Functional	Put a foam block in the door path while the doors close	Doors reverse before pressing hard on the block
E14	Negative	Hold the doors open past the timeout	Buzzer sounds; doors close slowly (nudging) if that feature exists
E15	Functional	Try to make the lift travel with the car door held open	Lift does not move while any door is open
E16	Functional	Observed during the technician's inspection: try the landing door on a floor where the car is not present	Landing door stays locked

Load

ID	Category	Test case	Expected result
E17	Boundary	Load the car to its rated load with test weights	Travels normally
E18	Boundary	Add weight just above the rated load	Overload buzzer and indicator; doors stay open; lift does not move
E19	Functional	Remove the extra weight	Overload warning clears; lift accepts calls again

Emergencies and service modes

ID	Category	Test case	Expected result
E20	Functional	Press and hold the alarm button	Alarm sounds and the intercom reaches security or the monitoring desk within the agreed time
E21	Negative	Cut mains power while the lift travels between floors	Emergency light works; if a rescue device is fitted, the car moves to the nearest floor and opens its doors
E22	Functional	Trigger the fire alarm signal in a controlled test	Lift goes to the designated floor, opens its doors and ignores normal calls, as the local code and spec require
E23	Negative	Simulate a fault that stops the car between floors	Doors do not open between floors; alarm and intercom still work; the fault is logged
E24	Functional	Technician switches the lift to maintenance mode	Landing calls ignored; landing displays show it is out of service

Access, accessibility and UI

ID	Category	Test case	Expected result
E25	Security	Show a card allowed for floor 10 only and press B	B refused; 10 accepted
E26	Security	Show an expired or blocked card	All restricted floors refused; event logged
E27	UI	Ride from G to 10 and back	Car and landing displays show the correct floor and direction at every floor
E28	UI	Arrive at a floor	Chime and voice announcement (if fitted) name the floor
E29	UI	Check button height and markings	Buttons reachable from a wheelchair; raised or Braille markings as specified
E30	UI	Press any button	It lights on press and goes off when the call is served

Performance

ID	Category	Test case	Expected result
E31	Performance	Morning peak simulation: many up calls from G with all lifts in service	Group control sends a suitable car; waiting time stays within the installer's figure
E32	Performance	Measure the step between car floor and landing at several floors, empty and loaded	Within the installer's levelling tolerance

What to prioritise

The cases that protect people come first: doors (E13, E15, E16), overload (E18) and emergencies (E20 to E23). A common mistake is to spend the whole answer on buttons and displays. Another is to forget the multiple-lift case: with two or more lifts, "which lift answers my call" is a requirement you should ask about.

Test cases for a lift / elevator