PyTest is a mature, feature-rich Python testing framework that makes writing tests simple and scalable.

Key differences from unittest:

• Simpler syntax: Uses plain assert statements vs self.assertEqual()
• Automatic test discovery: No need for test suites
• Rich plugin ecosystem: Extensive third-party support
• Fixtures: Powerful dependency injection system
• Parametrized testing: Built-in multiple input support
• Better error reporting: More detailed failure messages

# PyTest style
def test_addition():
    assert 2 + 2 == 4

# unittest style
import unittest
class TestMath(unittest.TestCase):
    def test_addition(self):
        self.assertEqual(2 + 2, 4)

Installation via pip:

pip install pytest

Running tests:

pytest                    # Run all tests
pytest test_file.py       # Run specific file
pytest -v                 # Verbose output
pytest -k "test_name"     # Run tests matching pattern

PyTest automatically discovers tests following these conventions:

• Test files: test_*.py or *_test.py
• Test functions: Functions starting with test_
• Test classes: Classes starting with Test (no __init__ method)
• Test methods: Methods in test classes starting with test_

# Valid test file: test_math.py
def test_addition():        # ✓ Discovered
    pass
class TestCalculator:       # ✓ Discovered
    def test_multiply(self): # ✓ Discovered
        pass
    def helper_method(self): # ✗ Not discovered
        pass

PyTest provides several ways to skip tests:

import pytest
@pytest.mark.skip(reason="Not implemented yet")
def test_feature():
    pass
@pytest.mark.skipif(sys.version_info < (3, 8), reason="Requires Python 3.8+")
def test_walrus_operator():
    pass
def test_conditional_skip():
    if not has_database_connection():
        pytest.skip("Database not available")