How is the correctness of task execution verified using tests?

Verification of the correctness of task execution through tests is carried out by writing and running test scenarios that check whether the code works according to the requirements. Tests compare the expected result with the actual one. If the results match, the test is considered passed; otherwise, it is failed.

For example, unit tests check the correctness of individual functions or methods. Integration tests check the interaction between components.

An example 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()

If all tests pass, it means the task has been correctly completed within the tested conditions.