Unit Testing

Introduction

Unit testing ensures code correctness through automated test cases.

Basic Test Case

import unittest

class TestMathOperations(unittest.TestCase):
    
    def test_addition(self):
        self.assertEqual(2 + 2, 4)
    
    def test_division(self):
        with self.assertRaises(ZeroDivisionError):
            1 / 0
    
    def test_list_operations(self):
        lst = [1, 2, 3]
        lst.append(4)
        self.assertEqual(lst, [1, 2, 3, 4])

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

Assertions

self.assertEqual(a, b)        # a == b
self.assertNotEqual(a, b)     # a != b
self.assertTrue(x)           # bool(x) is True
self.assertFalse(x)           # bool(x) is False
self.assertIsNone(x)          # x is None
self.assertIs(a, b)           # a is b (identity)
self.assertIn(x, coll)        # x in collection
self.assertAlmostEqual(a, b)   # a ≈ b (floating point)

Test Fixtures

class TestDatabase(unittest.TestCase):
    
    @classmethod
    def setUpClass(cls):
        cls.db = connect_database()
    
    def setUp(self):
        self.transaction = self.db.begin()
    
    def tearDown(self):
        self.transaction.rollback()
    
    @classmethod
    def tearDownClass(cls):
        cls.db.close()

Practice Problems

1. Test basic calculator operations
2. Test exception handling
3. Use setUp and tearDown
4. Test edge cases
5. Mock external dependencies