Python Pytest Module
pytest is a framework that makes building simple and scalable tests easy. Tests are expressive and readable—no boilerplate code required. It is often preferred over the standard unittest module for its simpler syntax and powerful features.
Installation
pip install pytestBasic Usage
Create a file named test_sample.py. Pytest identifies files starting with test_ or ending with _test.py as test files. Unlike unittest, you do not need to create a class.
def func(x):
return x + 1
def test_answer():
assert func(3) == 5Running Tests
Run the tests from the command line:
pytestFixtures
Fixtures provide a fixed baseline upon which tests can reliably and repeatedly execute. They are defined using the @pytest.fixture decorator.
import pytest
@pytest.fixture
def input_value():
return 39
def test_divisible_by_3(input_value):
assert input_value % 3 == 0
def test_divisible_by_6(input_value):
assert input_value % 6 == 0Parametrization
Parametrization allows you to run a test function multiple times with different arguments.
import pytest
@pytest.mark.parametrize("num, output", [(1, 11), (2, 22), (3, 33)])
def test_multiplication_11(num, output):
assert 11 * num == outputMarkers
Markers allow you to categorize tests (e.g., slow, smoke).
import pytest
@pytest.mark.slow
def test_slow_function():
import time
time.sleep(1)
assert TrueRun with pytest -m slow.
Testing Exceptions
Use pytest.raises() to assert that a block of code raises a specific exception.
import pytest
def test_zero_division():
with pytest.raises(ZeroDivisionError):
1 / 0