Why advanced patterns handle real-world complexity in PyTest - Test Execution Impact

Test Overview

This test checks a function that calculates discounts based on complex rules. It verifies that the function correctly applies multiple conditions, showing how advanced patterns help manage real-world complexity.

Test Code - pytest

PyTest

import pytest

def calculate_discount(price, customer_type, is_holiday):
    if price <= 0:
        return 0
    if customer_type == 'VIP' and is_holiday:
        return price * 0.3
    elif customer_type == 'VIP':
        return price * 0.2
    elif is_holiday:
        return price * 0.1
    else:
        return 0


def test_calculate_discount():
    # VIP customer on holiday
    assert calculate_discount(100, 'VIP', True) == 30
    # VIP customer not on holiday
    assert calculate_discount(100, 'VIP', False) == 20
    # Regular customer on holiday
    assert calculate_discount(100, 'Regular', True) == 10
    # Regular customer not on holiday
    assert calculate_discount(100, 'Regular', False) == 0
    # Zero price
    assert calculate_discount(0, 'VIP', True) == 0
    # Negative price
    assert calculate_discount(-50, 'VIP', True) == 0

Execution Trace - 8 Steps

Step	Action	System State	Assertion	Result
1	Test starts	pytest test runner initialized	-	PASS
2	Calls calculate_discount(100, 'VIP', True)	Function evaluates conditions for VIP customer on holiday	Return value equals 30	PASS
3	Calls calculate_discount(100, 'VIP', False)	Function evaluates conditions for VIP customer not on holiday	Return value equals 20	PASS
4	Calls calculate_discount(100, 'Regular', True)	Function evaluates conditions for regular customer on holiday	Return value equals 10	PASS
5	Calls calculate_discount(100, 'Regular', False)	Function evaluates conditions for regular customer not on holiday	Return value equals 0	PASS
6	Calls calculate_discount(0, 'VIP', True)	Function evaluates zero price case	Return value equals 0	PASS
7	Calls calculate_discount(-50, 'VIP', True)	Function evaluates negative price case	Return value equals 0	PASS
8	Test ends	All assertions passed	-	PASS

Failure Scenario

Failing Condition: Function returns incorrect discount for VIP customer on holiday

Execution Trace Quiz - 3 Questions

What discount does a VIP customer get on a holiday for a price of 100?

A 10

B 20

C 30

D 0

Key Result

Using multiple conditions and test cases helps cover real-world scenarios, ensuring the function behaves correctly under complex rules.