To unit test your code, you need to install the package pytest: $ python3 -m pip install --user pytest $ ln -s /Users/mtitek/Library/Python/3.11/bin/pytest /usr/local/bin/pytest
Assertions: are used to validate conditions in the unit tests

• assert output: Assert that 'output' is True
• assert not output: Assert that 'output' is False
• assert output == value: Assert that 'output' is equal to 'value'
• assert output != value: Assert that 'output' is not equal to 'value'
• assert output in collection: Assert that 'output' is an item in the collection 'collection'
• assert output not in collection: Assert that 'output' is not an item in the collection 'collection'

Simple unit test:
Create a file hello.py that contains a simple function 'hello': #hello.py def hello(name): if(name == ''): return 'undefined' else: return name
Create a unit test file test_hello.py: #test_hello.py from hello import hello def test_hello(): """hello unit test""" output = hello('') assert output == 'undefined' output = hello('abc') assert output == 'abc'
To execute the unit test, open a terminal and run 'pytest' command from the project folder: $ pytest =============================================== test session starts ================================================ platform darwin -- Python 3.11.4, pytest-7.4.0, pluggy-1.2.0 rootdir: /Users/mtitek/python collected 1 item test_hello.py . [100%] ================================================ 1 passed in 0.01s =================================================
If there's an error in the unit test, you should see: $ pytest =============================================== test session starts ================================================ platform darwin -- Python 3.11.4, pytest-7.4.0, pluggy-1.2.0 rootdir: /Users/mtitek/python collected 1 item test_hello.py F [100%] ===================================================== FAILURES ===================================================== ____________________________________________________ test_hello ____________________________________________________ def test_hello(): """hello unit test""" output = hello('') assert output == 'undefined' output = hello('abc') > assert output == 'foo' E AssertionError: assert 'abc' == 'foo' E - foo E + abc test_hello.py:9: AssertionError ============================================= short test summary info ============================================== FAILED test_hello.py::test_hello - AssertionError: assert 'abc' == 'foo' ================================================ 1 failed in 0.05s =================================================
Using fixtures: @pytest.fixture
They allow you to mockup classes and inject them dynamically in your unit tests.

Create a file addition.py that contains a simple class 'Addition': #addition.py class Addition: def __init__(self, i, j): self.i = i self.j = j def add(self): return self.i + self.j
Create a unit test file test_addition.py: #test_addition.py import pytest from addition import Addition @pytest.fixture def addition(): addition = Addition(4, 6) return addition def test_add(addition): """add unit test""" output = addition.add() assert output == 10
To execute the unit test, open a terminal and run 'pytest' command from the project folder: $ pytest =============================================== test session starts ================================================ platform darwin -- Python 3.11.4, pytest-7.4.0, pluggy-1.2.0 rootdir: /Users/mtitek/python collected 1 item test_addition.py . [100%] ================================================ 1 passed in 0.01s =================================================