What is the hardest part of a booking system to test?

Two people trying to book the same last seat at the same moment (T09), and the gap between payment success and ticket confirmation (T21). Both need controlled test data and usually an API or tool to create the timing; clicking in two browsers is not reliable.

Should I quote real IRCTC or airline rules in an interview?

Only if you are sure and say they can change. It is safer to say 'the operator's current advance-booking window and refund rules' and show how you would test them as boundaries.

Test cases for ticket booking (train, flight, movie)

Written for a booking app that can sell train, flight or movie tickets; rows that apply to only one kind say so. All rules below (advance booking window, seats per booking, hold time, refund cut-offs) are examples: operators set their own and change them, so take the real values from the current rules before running.

How to answer in an interview

Ask first: which kind of tickets, is there seat selection, how long is a seat held during payment, how many seats per booking, are there quotas or waitlists, what are the cancellation and refund rules, and what happens at peak times such as the opening of a sale? Then follow the user journey: search, choose seats, passenger details, fare and payment, confirmation and ticket, cancellation. Close with concurrency and peak load, which is where booking systems usually fail.

Scope and test data

Example rules: bookings open up to 60 days ahead; at most 6 seats per booking; selected seats are held for 10 minutes. Test passengers use obviously fake names and contacts (Asha Test, [email protected], 9000000001). Payment uses the provider's sandbox and its published test methods only. Concurrency and peak-load cases need a test environment and tooling agreed with the team. These are designed cases, not an execution report.

Search

ID	Category	Test case	Expected result
T01	Functional	Search Delhi to Mumbai for a date next week	Results with times, availability and price
T02	Negative	Search with the same source and destination	Validation message; no search sent
T03	Negative	Pick yesterday's date	Past dates cannot be chosen
T04	Boundary	Pick the last day of the booking window, then the day after	Last day searchable; the day after blocked with a message
T05	Negative	Search a route or date with no services	Clear "no results" with a way to change the date
T06	Functional	Use the swap button	Source and destination swap; results refresh

Seat selection and holds

ID	Category	Test case	Expected result
T07	UI	Open the seat map	Available, booked and held seats look different; a legend explains them
T08	Boundary	Select 6 seats, then a 7th	6 allowed; the 7th blocked with a message
T09	Functional	Two test users try to book the same last seat at the same time	Exactly one gets it; the other is told and can pick again
T10	Boundary	Hold seats and wait past 10 minutes without paying	Seats released; user told; payment on the expired hold is refused
T11	Functional	Movie: leave a single empty seat between booked seats, if the cinema forbids it	Blocked with an explanation, or allowed, as the rule says
T12	Functional	Train: choose a berth preference	Shown as a preference, not a guarantee, unless the rules say otherwise

Passenger details

ID	Category	Test case	Expected result
T13	Boundary	Enter ages at each fare boundary (child, adult, senior)	Fare category switches exactly at the boundary in the rules
T14	Negative	Leave the name empty; enter digits in the name	Validation messages next to the field
T15	Functional	Flight: add an infant on an adult's lap	Infant fare applied; infant linked to that adult
T16	Functional	Flight: enter the ID details the airline requires	Fields required and validated as per the airline's rules
T17	Functional	Enter contact `[email protected]` and `9000000001`	Ticket and updates go to these contacts in the test environment

Fare and payment

ID	Category	Test case	Expected result
T18	Functional	Check the fare breakdown	Base fare, taxes and fees add up to the total charged
T19	Functional	Apply a valid, an expired and a not-applicable promo code	Valid code reduces the total; others show a specific reason
T20	Functional	Pay successfully with a sandbox method	Booking ID or PNR generated; seats marked booked; confirmation sent
T21	Negative	Payment succeeds but the booking call times out	Booking completed later by reconciliation, or an automatic refund; the user is told which
T22	Negative	Payment fails	No ticket; seats stay held until expiry or are released; user can retry
T23	Negative	Double-click Pay, or press Back and Pay again	One charge and one booking

Waitlist and availability

ID	Category	Test case	Expected result
T24	Functional	Train: book when only waitlist is available	Status shows the waitlist position before and after payment
T25	Functional	Train: a confirmed passenger cancels	Waitlisted bookings move up as the rules say; status updates for the user
T26	Functional	Show or flight fully sold	Sold-out state; no seat selection or payment possible

Cancellation and changes

ID	Category	Test case	Expected result
T27	Functional	Cancel before the refund cut-off	Refund amount shown before confirming; refund matches it
T28	Boundary	Cancel just before and just after the cut-off	Refund changes exactly at the cut-off
T29	Functional	Cancel one of three passengers	Only that passenger cancelled; refund for that share only
T30	Functional	Flight: change to another date	Fare difference and fees shown and charged correctly

Ticket, security and performance

ID	Category	Test case	Expected result
T31	Functional	Open the e-ticket and booking history	Passenger, seat, date, time and booking ID correct; QR code scans in the test scanner
T32	Security	Change the booking ID in the ticket URL or API to another user's	Access denied; no ticket details shown
T33	Security	Send many search or booking requests from one client quickly	Rate limit or challenge as specified; normal users unaffected
T34	Performance	Simulate the opening of a popular sale with many users	Queueing or throttling works; no seat sold twice; no payment without a booking outcome
T35	Functional	Flight: book a route across time zones	Departure and arrival shown in each airport's local time and labelled

What to prioritise

T09, T10, T21, T23 and T34: each can sell one seat twice or take money without a ticket. In an interview, many candidates list only the happy path and form validation. Mention concurrency and the payment-to-confirmation gap, and say how you would create them in a test environment.