Seth Barrett

Daily Blog Post: January 31st, 2023


Jan 31st, 2023

Getting Started with Unit Testing in Python

The unittest module is a built-in Python library that allows for the creation and execution of unit tests. Unit tests are individual tests that check the functionality of specific parts of your code, usually individual functions or methods. These tests help to ensure that your code is working correctly and that any changes you make in the future won't break any existing functionality. Many companies require a working knowledge of unit testing for the programming languages they use, and testing is an important part of software engineering. This post will teach you the basics of unit testing and Python, and this knowledge carries over to most other programming languages that companies use in production code.

Here are some of the most commonly used methods in the unittest module:

  • assertEqual(a, b): This method checks if the values of a and b are equal. If they are not, it raises an AssertionError.

import unittest

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

class TestAdd(unittest.TestCase):

    def test_add(self):
        self.assertEqual(add(3, 4), 7)
        self.assertEqual(add(-2, 5), 3)
        self.assertEqual(add(0, 0), 0)

  • assertTrue(x): This method checks if the value of x is True. If it is not, it raises an AssertionError.

import unittest

def is_even(x):
    return x % 2 == 0

class TestIsEven(unittest.TestCase):

    def test_is_even(self):

  • assertRaises(exception, function, *args): This method checks if the specified function raises the specified exception when called with the specified args. If the function does not raise the exception, it raises an AssertionError.

import unittest

def divide(a, b):
    return a / b

class TestDivide(unittest.TestCase):

    def test_divide(self):
        self.assertRaises(ZeroDivisionError, divide, 5, 0)

  • setUp() and tearDown(): These methods are run before and after each test method in the test case, respectively. They can be used to set up any required resources or clean up after a test.

import unittest

class TestStringMethods(unittest.TestCase):

    def setUp(self):
        self.string = "hello world"

    def test_upper(self):
        self.assertEqual(self.string.upper(), "HELLO WORLD")

    def test_isupper(self):

    def tearDown(self):
        del self.string

It's important to note that the unittest library is not the only option for unit testing in Python. Other popular testing frameworks include pytest and doctest.

You can run the unit test by running the python file with the command python -m unittest <file_name>

I hope this gives you a good overview of the unittest module and its associated methods. Let me know if you have any questions or need more examples.