5A-unit-tests

Python Unit Tests

Unit Tests

A unit is the smallest testable part of an application, typically a function, method, or class. The goal of unit testing is to validate that each unit of the software performs as designed.

In the context of Python, unit testing is often done using the built-in unittest module or third-party libraries like pytest.

Unit testing with python library pytest.

Install pytest.

pip install pytest

We use the python assert keyword for this purpose.

Assert Keyword

In Python, the assert keyword is used to test a condition as a debugging aid. It takes an expression, and if the expression is False, it raises an AssertionError exception with an optional error message. If the expression is True, the program continues execution.

Here's a simple example:

x = 10

assert x > 0, "x should be a positive number"

In this example, if x is not greater than 0, the assert statement will raise an AssertionError with the message "x should be a positive number." This is particularly useful during development to catch logical errors or unexpected conditions early in the code. However, it's important to note that using assert for data validation in production code is not recommended, as it can be disabled globally, and unexpected failures may lead to security vulnerabilities.

To test the code using pytest.

instead of executing file with python, execute it with pytest.

Run tests:

Here is an example for the unit_tests.py file in this directory.

pytest 6B-unit-tests/unit_tests.py

Using unittest

The unittest module is part of the Python standard library and provides a more comprehensive testing framework. It supports test automation, sharing of setup and shutdown code for tests, aggregation of tests into collections, and more.

Here's an example of using unittest:

import unittest

def add(x, y):
    return x + y

class TestAdd(unittest.TestCase):
    def test_add(self):
        self.assertEqual(add(1, 2), 3)
        self.assertEqual(add(0, 0), 0)
        self.assertEqual(add(-1, 1), 0)


if __name__ == '__main__':
    unittest.main()

In this example, we define a simple add function and a TestAdd class that inherits from unittest.TestCase. We then define a test method test_add that uses various assert methods provided by unittest.TestCase to check the behavior of the add function.

Run tests:

To run the tests, you can execute the script directly, and unittest will discover and run the tests:

python test_add.py