Validating Functions

Unit tests verify that isolated parts of you're code perform as expected. Consider a function that concatenates user details:

def assemble_username(given_name, surname, nickname=''):
    """Constructs a standardized username."""
    if nickname:
        user_str = f"{given_name} '{nickname}' {surname}"
    else:
        user_str = f"{given_name} {surname}"
    return user_str.title()

To test this logic, the unittest module provides a framework for creating test cases. You can define a class that inherits from unittest.TestCase and write methods to check various inputs:

import unittest

class TestUsernameAssembly(unittest.TestCase):
    def test_basic_name(self):
        result = assemble_username('alan', 'turing')
        self.assertEqual(result, 'Alan Turing')

    def test_name_with_nickname(self):
        result = assemble_username('edward', 'norton', 'ed')
        self.assertEqual(result, "Edward 'Ed' Norton")

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

Core Assertion Methods

The unittest module includes several built-in assertion methods to evaluate conditions:

• assertEqual(a, b): Verifies that a is equal to b.
• assertNotEqual(a, b): Verifies that a is not equal to b.
• assertTrue(x): Verifies that x evaluates to True.
• assertFalse(x): Verifies that x evaluates to False.
• assertIn(item, collection): Veriifes that item exists within collection.
• assertNotIn(item, collection): Verifies that item is absent from collection.

Validating Classes

When testing classes, you instantiate the class and verify its methods functon correctly. Below is a class designed to gather feedback:

class FeedbackCollector:
    def __init__(self, subject):
        self.subject = subject
        self.comments = []

    def record_comment(self, comment):
        self.comments.append(comment)

    def fetch_comments(self):
        return self.comments

A basic test case for this class creates an instance and asserts that a stored comment is present:

import unittest
from feedback import FeedbackCollector

class TestFeedbackCollector(unittest.TestCase):
    def test_record_single_comment(self):
        collector = FeedbackCollector("Service Quality")
        collector.record_comment("Excellent service")
        self.assertIn("Excellent service", collector.comments)

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

Utilizing the setUp Method

Creating instances repeatedly in every test method leads to redundancy. The setUp() method executes before each test, allowing you to establish a shared state:

import unittest
from feedback import FeedbackCollector

class TestFeedbackCollectorWithSetup(unittest.TestCase):
    def setUp(self):
        self.collector = FeedbackCollector("App Usability")
        self.initial_comments = ["Great UI", "Needs dark mode", "Fast response"]

    def test_record_single_comment(self):
        self.collector.record_comment("Intuitive layout")
        self.assertIn("Intuitive layout", self.collector.comments)

    def test_record_multiple_comments(self):
        for comment in self.initial_comments:
            self.collector.record_comment(comment)
        for comment in self.initial_comments:
            self.assertIn(comment, self.collector.comments)

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