Python Testing with pytest: From First Test to Fixtures
Pytest changed how I write tests. Here is the progression from basic tests to fixtures, parametrization, and markers. I wrote tests with the unittest module for years before trying pytest . The switch was immediate. pytest tests are plain functions, assertions use the assert keyword, and the failure output shows exactly what went wrong. The barrier to writing a test dropped from writing a class with setup and teardown methods to writing a three-line function. That lower barrier meant I wrote more tests. Writing a Basic Test A pytest test is a function whose name starts with test_ . The assertion is a plain assert statement. No framework classes, no self.assertEqual. just Python. def test_addition(): assert 1 + 1 == 2 def test_string_upper(): assert 'hello'.upper() == 'HELLO' def test_list_contains(): assert 3 in [1, 2, 3] When an assertion fails, pytest shows the values on both sides. This is more informative than unittest's AssertionError with no context. The output includes the expression, the expected value, and the actual value. Running Tests Run pytest in the project directory and it discovers tests automatically. Files named test_*.py or *_test.py are scanned…