Mastering Pytest: Automated Testing, Fixtures & Parametrization for Python

Why Pytest is the Industry Standard Testing Framework

Modern Python engineering teams use Pytest for its concise syntax, powerful fixture dependency injection system, and rich plugin ecosystem. Unlike standard unittest, Pytest avoids boilerplate class hierarchies.

1. Pytest Fixtures with Yield Teardown

import pytest

@pytest.fixture
def sample_database():
    # Setup connection
    db = {"users": [], "connected": True}
    print("
[Setup] Connected to mock DB")
    yield db
    # Teardown
    db["connected"] = False
    print("[Teardown] Closed mock DB connection")

def test_insert_user(sample_database):
    sample_database["users"].append("Kashinath")
    assert len(sample_database["users"]) == 1
    assert "Kashinath" in sample_database["users"]

2. Test Parametrization (`@pytest.mark.parametrize`)

import pytest

def calculate_discount(price: float, is_student: bool) -> float:
    return price * 0.8 if is_student else price

@pytest.mark.parametrize("price, is_student, expected", [
    (100.0, True, 80.0),
    (100.0, False, 100.0),
    (50.0, True, 40.0),
    (0.0, True, 0.0),
])
def test_discounts(price, is_student, expected):
    assert calculate_discount(price, is_student) == expected