Did you write unit tests yourself or was testing done by another team?

In my practice, I have written unit tests myself because I consider it an important part of developing quality code. It helps identify errors early and facilitates maintenance.

Here's an example of a simple unit test in Python using unittest:

import unittest

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

class TestAddFunction(unittest.TestCase):
    def test_add_positive_numbers(self):
        self.assertEqual(add(2, 3), 5)

    def test_add_negative_numbers(self):
        self.assertEqual(add(-1, -1), -2)

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

In some teams, testing may be done by dedicated QA engineers, but integrating unit tests into the development process significantly improves product quality.