What questions should I ask before testing a water bottle?

What it is made of, its capacity, who uses it (school, gym, office, travel), whether it is insulated and what temperature claims it makes, what lid type it has, whether it is dishwasher safe, and the price range. Each answer adds or removes cases.

Is checking the label really a test case?

Yes. A label that says 1 litre on a bottle that holds 900 ml, or that leaves out care instructions, is a defect the customer will notice. Mandatory declarations are also a legal requirement in most markets.

Test cases for a water bottle (interview question)

Assumes a 1 litre double-wall stainless steel insulated bottle with a screw cap and a flip-top drinking spout, sold for office and travel use. The product claims (hours hot, hours cold, leak-proof, dishwasher-safe lid) are examples; use the real claims on the box.

How to answer in an interview

Ask first: what material, what capacity, for whom, insulated or not, what lid, what claims does the box make, and is it for children? A plastic school bottle and a steel flask need different tests. Then cover: capacity and pouring, leaks, temperature, durability, hygiene and safety, usability, and labelling. Close with the cases you would run first.

Scope and test data

Test several bottles from more than one batch. Use a kitchen thermometer, a measuring jug, a stopwatch and a padded drop area. Agree every limit in advance (for example "above the box's stated temperature after the stated hours"); without a stated limit, record the measurement instead of passing or failing. These are designed cases, not an execution report.

Capacity and pouring

ID	Category	Test case	Expected result
W01	Functional	Fill to the brim with a measuring jug	Holds the stated 1 litre, within the tolerance in the spec
W02	Functional	Fill to any printed volume mark and measure	Mark is accurate within tolerance
W03	Functional	Pour into a glass from the wide mouth	Smooth flow; no water runs down the outside
W04	Functional	Drink through the flip-top spout	Comfortable flow without having to squeeze or tilt fully
W05	UI	Open and close the flip-top with one hand	Possible without the other hand

Leaks

ID	Category	Test case	Expected result
W06	Functional	Fill, close fully and hold upside down for one minute	No drip from the cap or spout
W07	Functional	Fill, close and shake hard	No leak
W08	Functional	Lay the full, closed bottle on its side in a bag for 8 hours	Bag stays dry
W09	Negative	Close the cap only partly, then tilt	Partial closure is easy to see or feel; any leak is noted against the leak-proof claim
W10	Negative	Fill with a fizzy drink, close and shake, if carbonated drinks are not ruled out	Cap does not fly off; if not supported, the label warns against it

Temperature

ID	Category	Test case	Expected result
W11	Functional	Fill with hot water at the temperature on the box, close, measure after the stated hours	Temperature still meets the hot-hours claim
W12	Functional	Fill with ice water, close, measure after the stated hours	Temperature still meets the cold-hours claim
W13	Functional	Hold the bottle filled with hot water	Outside is not hot to touch (double wall works)
W14	Functional	Fill with ice water on a humid day	No condensation on the outside
W15	Negative	Put the bottle in a freezer, if not prohibited	If the label warns against it, the warning is present; if allowed, no crack or bulge

Durability

ID	Category	Test case	Expected result
W16	Negative	Drop the full bottle from one metre onto a hard floor	No leak; cap stays on; a dent is acceptable only if the spec says so
W17	Functional	Open and close the flip-top hinge many times (agreed count)	Hinge still snaps shut and seals
W18	Functional	Screw and unscrew the cap many times	Threads do not wear; seal still holds
W19	Negative	Tighten the cap much harder than normal	No thread stripping; cap still opens by hand
W20	Functional	Run the lid through the dishwasher the agreed number of times, if dishwasher-safe is claimed	No warping; seal still holds; print does not fade
W21	Functional	Scratch the outer coating lightly with a key and wash it	Coating does not peel

Hygiene and safety

ID	Category	Test case	Expected result
W22	Security	Check the food-contact material documents for the target market	Certificates present and current for every part that touches the drink
W23	Functional	Fill with water for 24 hours, then smell and taste	No plastic or metallic smell or taste
W24	Functional	Remove the gasket and spout for cleaning	All parts come out and go back without tools; a bottle brush reaches the bottom
W25	Security	Run a finger around the mouth and spout	No sharp edges
W26	Security	For a children's version, try to detach small parts	Small parts do not come off in normal use

Usability and labelling

ID	Category	Test case	Expected result
W27	Compatibility	Put the bottle in a car cup holder, a bicycle bottle cage and a backpack side pocket	Fits the ones the product claims
W28	UI	Hold the bottle with wet hands	Does not slip easily
W29	Functional	Drop ice cubes through the mouth	Standard ice cubes fit
W30	Functional	Weigh the empty bottle	Matches the stated weight
W31	UI	Read the label and box	Capacity, material, care instructions, MRP and other mandatory declarations are present and legible

What to prioritise

Leaks (W06 to W08) and the temperature claims (W11, W12) are what customers complain about and what the box promises. In an interview the common mistake is to skip clarifying questions and test a generic bottle; asking "insulated or plastic, and for whom?" first is usually what the interviewer is waiting for.

Test cases for a water bottle