Add TDD assignment questions for booking system

Added TDD assignment questions for a hotel room booking system, covering basic operations, modifications, pricing, and advanced features.

Author: Carrington-dev

examples/with-unittest/booking_system/README.md

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+Here are some TDD assignment questions for a booking system:
+
+## Assignment: Hotel Room Booking System (TDD Approach)
+
+### Part 1: Basic Booking Operations
+
+**Question 1: Create a Booking**
+Implement functionality to create a new booking. A booking should have:
+- Guest name
+- Room number
+- Check-in date
+- Check-out date
+- Booking reference (auto-generated unique ID)
+
+Write tests first that verify:
+- A booking can be created with valid data
+- Booking reference is automatically generated and unique
+- Check-out date must be after check-in date
+- Required fields cannot be empty
+
+**Question 2: Check Room Availability**
+Implement a method to check if a room is available for given dates.
+
+Write tests for:
+- Room is available when no bookings exist
+- Room is unavailable when dates overlap with existing booking
+- Room is available when requested dates are before/after existing bookings
+- Same-day checkout and check-in (checkout at 11am, new checkin at 2pm) - decide and test your business rule
+
+**Question 3: Prevent Double Booking**
+Implement logic to prevent booking a room that's already reserved.
+
+Write tests for:
+- Cannot book room with exact same dates as existing booking
+- Cannot book room when dates partially overlap
+- Cannot book room when new booking spans existing booking
+- Cannot book room when new booking is contained within existing booking
+- Can book room for different dates
+
+### Part 2: Booking Modifications
+
+**Question 4: Cancel a Booking**
+Implement booking cancellation functionality.
+
+Write tests for:
+- Successfully cancel an existing booking
+- Room becomes available after cancellation
+- Cannot cancel a booking that doesn't exist
+- Cannot cancel an already cancelled booking
+- Cancelled bookings are marked (not deleted) for audit purposes
+
+**Question 5: Modify Booking Dates**
+Implement functionality to change check-in/check-out dates of existing booking.
+
+Write tests for:
+- Successfully modify dates when room is available
+- Cannot modify if new dates overlap with another booking
+- Cannot modify to invalid dates (checkout before checkin)
+- Original booking is updated, not duplicated
+
+### Part 3: Pricing & Calculations
+
+**Question 6: Calculate Booking Cost**
+Implement cost calculation based on number of nights and room rate.
+
+Write tests for:
+- Single night stay calculation
+- Multiple night stay calculation
+- Different room rates (standard: $100, deluxe: $150, suite: $200)
+- Zero or negative duration returns error
+
+**Question 7: Apply Discounts**
+Implement discount logic for bookings.
+
+Write tests for:
+- 10% discount for stays of 7+ nights
+- 15% discount for stays of 14+ nights
+- Weekend surcharge: 20% extra for Friday/Saturday nights
+- Discounts and surcharges are calculated correctly together
+
+**Question 8: Calculate Refund Amount**
+Implement cancellation refund policy.
+
+Write tests for:
+- Full refund if cancelled 7+ days before check-in
+- 50% refund if cancelled 3-6 days before check-in
+- No refund if cancelled within 2 days of check-in
+- No refund for cancellations after check-in date
+
+### Part 4: Advanced Features
+
+**Question 9: List Bookings**
+Implement methods to retrieve bookings with filters.
+
+Write tests for:
+- Get all bookings for a specific room
+- Get all bookings for a specific guest
+- Get all bookings within a date range
+- Get upcoming bookings only (future check-ins)
+- Get active bookings (currently checked in)
+
+**Question 10: Room Capacity Management**
+Implement guest count validation (assume rooms have max capacity).
+
+Write tests for:
+- Room capacity limits (standard: 2, deluxe: 3, suite: 4)
+- Cannot book with more guests than room capacity
+- Can book with fewer guests than capacity
+- Extra guest fee: $25/night per guest above 2
+
+**Question 11: Seasonal Pricing**
+Implement dynamic pricing based on season.
+
+Write tests for:
+- Peak season (Dec-Feb, Jun-Aug): 1.5x base rate
+- Off-peak season (Mar-May, Sep-Nov): base rate
+- Calculate total cost correctly when booking spans seasons
+- Weekend surcharge applies to seasonal rate
+
+**Question 12: Waitlist Management**
+When room is unavailable, add guest to waitlist.
+
+Write tests for:
+- Add guest to waitlist when room unavailable
+- Notify/promote first waitlisted guest when booking cancelled
+- Remove from waitlist when they book different dates
+- Waitlist ordered by request date (first come, first served)
+
+---
+
+## Bonus Challenges
+
+**Question 13: Multiple Room Booking**
+Allow booking multiple rooms in single reservation.
+
+**Question 14: Loyalty Points**
+Award points: 10 points per dollar spent, implement redemption (100 points = $1 discount).
+
+**Question 15: Payment Status Tracking**
+Track payment status: pending, partial, paid, refunded with state transitions.
+
+---
+
+## Instructions
+
+For each question:
+1. **Write the test first** (Red phase)
+2. **Make it pass with minimal code** (Green phase)
+3. **Refactor** for clean code (Refactor phase)
+4. Run all previous tests to ensure nothing broke
+
+Start simple with Question 1 and progress sequentially. Each question builds on previous functionality.
+
+Which questions would you like to start with?