README.md

Mass Transit Billing System

Overview

Calculates user bills for a mass transit system based on journey data, applying zone-based pricing and daily/monthly caps

Task Requirements

1. Produce production-quality code with tests
2. Take command line arguments for input/output files
3. Calculate total charge for each customer's transit journeys
4. Apply pricing rules:

• £2 base fee per journey
• Additional zone-based costs:

Zone 1: £0.80 Zones 2-3: £0.50 Zones 4-5: £0.30 Zone 6+: £0.10

• £5 fee for erroneous journeys
• Daily cap: £15
• Monthly cap: £100

Requirements

• Python 3.7+
• pytest (for testing)

Usage

python main.py <zones_file_path> <journey_data_path> <output_file_path>

Example:

python main.py zone_map.csv journey_data.csv billing_results.csv

Testing

Run tests with:

pytest tests.py

Test Descriptions

1. test_read_zone_map: Validates correct reading of zone map from CSV
2. test_read_zone_map_invalid_data: Checks handling of invalid zone data
3. test_read_journey_data: Verifies correct reading of journey data
4. test_read_journey_data_invalid_station: Tests handling of unknown stations
5. test_calculate_journey_cost: Checks journey cost calculations for various zones
6. test_daily_cap: Ensures daily spending cap (£15) is applied correctly
7. test_monthly_cap: Verifies monthly spending cap (£100) is applied correctly
8. test_incomplete_journey: Checks application of incomplete journey fee (£5)
9. test_cross_midnight_journey: Verifies handling of journeys spanning midnight
10. test_export_billing_results: Checks correct formatting of billing results CSV

Assumptions

• Valid journeys completed before midnight
• £2 base fee per journey
• £5 fee for incomplete journeys
• Daily cap: £15, Monthly cap: £100
• Input data is chronologically sorted