🧪 Pytest Basics

Modern Python Testing

Testing with Pytest

Pytest is Python's most popular testing framework. Write simple, scalable test cases with minimal boilerplate.

💻 Getting Started

# pip install pytest

# calculator.py
def add(a, b):
    return a + b

def subtract(a, b):
    return a - b

# test_calculator.py
import pytest
from calculator import add, subtract

def test_add():
    assert add(2, 3) == 5
    assert add(-1, 1) == 0
    assert add(0, 0) == 0

def test_subtract():
    assert subtract(5, 3) == 2
    assert subtract(0, 5) == -5

# Run: pytest
# Run specific file: pytest test_calculator.py
# Verbose: pytest -v

🔧 Fixtures & Parametrize

# Fixtures (setup/teardown)
@pytest.fixture
def sample_data():
    return [1, 2, 3, 4, 5]

def test_sum(sample_data):
    assert sum(sample_data) == 15

# Parametrized tests
@pytest.mark.parametrize("a, b, expected", [
    (2, 3, 5),
    (0, 0, 0),
    (-1, 1, 0),
    (10, 5, 15)
])
def test_add_multiple(a, b, expected):
    assert add(a, b) == expected

# Test exceptions
def test_division_by_zero():
    with pytest.raises(ZeroDivisionError):
        result = 1 / 0

🎯 Key Takeaways