Can you explain what is meant by unit testing of code?

Unit testing is the process of verifying individual parts (modules) of code for correctness. Each module is tested in isolation from the rest of the system to ensure it performs its function correctly.

The goal of unit testing is to identify errors early in development, facilitate debugging, and improve code quality.

Example in Python using unittest:

import unittest

def add(a, b):
    return a + b

class TestMathFunctions(unittest.TestCase):
    def test_add(self):
        self.assertEqual(add(2, 3), 5)
        self.assertEqual(add(-1, 1), 0)

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

Here, the add function is tested separately to ensure its correctness.