Python Testing with unittest and pytest
Testing is a crucial part of software development. Python provides built-in tools like unittest and supports powerful third-party frameworks like pytest.
unittest
unittest is the unit testing framework included in the Python standard library. It is inspired by JUnit and supports test automation, sharing of setup and shutdown code for tests, aggregation of tests into collections, and independence of the tests from the reporting framework.
Basic Example
To create a test case, you subclass unittest.TestCase.
import unittest
def add(x, y):
return x + y
class TestAddFunction(unittest.TestCase):
def test_add_integers(self):
self.assertEqual(add(1, 2), 3)
def test_add_floats(self):
self.assertAlmostEqual(add(1.1, 2.2), 3.3, places=1)
def test_add_strings(self):
self.assertEqual(add('a', 'b'), 'ab')
if __name__ == '__main__':
unittest.main()Common Assertions
assertEqual(a, b)assertNotEqual(a, b)assertTrue(x)assertFalse(x)assertIn(item, list)assertRaises(Error, func, args)
pytest
pytest is a mature, full-featured Python testing tool that helps you write better programs. It is often preferred over unittest because of its simpler syntax and powerful features like fixtures.
Installation
pip install pytestBasic Example
With pytest, you don't need classes. You just write functions that start with test_.
# test_sample.py
def add(x, y):
return x + y
def test_add_integers():
assert add(1, 2) == 3
def test_add_strings():
assert add('a', 'b') == 'ab'Fixtures
Fixtures are a powerful feature in pytest for setting up the environment for your tests (e.g., database connections, temporary files).
import pytest
@pytest.fixture
def sample_data():
return {"key": "value"}
def test_data(sample_data):
assert sample_data["key"] == "value"