Testing vs debugging distinction in Testing Fundamentals - Test Execution Compared

Test Overview

This test checks the difference between testing and debugging by simulating a simple test that finds a bug and then the debugging step to fix it. It verifies that testing detects the problem and debugging resolves it.

Test Code - unittest

Testing Fundamentals

import unittest

class Calculator:
    def add(self, a, b):
        return a + b

    def subtract(self, a, b):
        # Bug: mistakenly adds instead of subtracting
        return a + b

class TestCalculator(unittest.TestCase):
    def test_subtract(self):
        calc = Calculator()
        result = calc.subtract(5, 3)
        self.assertEqual(result, 2, "Subtract method should return difference")

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

Execution Trace - 7 Steps

Step	Action	System State	Assertion	Result
1	Test starts by importing unittest and defining Calculator class with add and subtract methods	Code loaded in memory, no errors yet	-	PASS
2	Test case TestCalculator.test_subtract is executed	Calculator instance created, subtract method called with (5,3)	Check if subtract(5,3) equals 2	FAIL
3	Test framework reports failure because subtract returned 8 instead of 2	Test report shows failure with message 'Subtract method should return difference'	AssertionError: 8 != 2	FAIL
4	Developer starts debugging by inspecting subtract method code	Code shows subtract method incorrectly adds instead of subtracting	-	PASS
5	Developer fixes subtract method to return a - b	Code updated, subtract method now correct	-	PASS
6	Test case re-run after fix	subtract(5,3) returns 2 as expected	Check if subtract(5,3) equals 2	PASS
7	Test framework reports test passed	Test report shows all tests passed	-	PASS

Failure Scenario

Failing Condition: subtract method incorrectly adds numbers instead of subtracting

Execution Trace Quiz - 3 Questions

What does the test detect in this example?

A A syntax error in the code

B A missing test case

C A bug in the subtract method

D A performance issue

Key Result

Testing helps find problems by checking expected behavior, while debugging is the process of finding and fixing the cause of those problems.