Test-driven development (TDD) concept in Testing Fundamentals - Test Execution Trace

Test Overview

This test demonstrates the Test-driven development (TDD) approach by first writing a test for a simple function that adds two numbers, then implementing the function to pass the test.

Test Code - unittest

Testing Fundamentals

import unittest

# Step 1: Write the test first
class TestAddFunction(unittest.TestCase):
    def test_add_two_numbers(self):
        result = add(2, 3)
        self.assertEqual(result, 5)

# Step 2: Implement the function to pass the test
def add(a, b):
    return a + b

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

Execution Trace - 5 Steps

Step	Action	System State	Assertion	Result
1	Test runner starts and discovers test_add_two_numbers	Test framework ready to run tests	-	PASS
2	test_add_two_numbers calls add(2, 3)	Function add is called with inputs 2 and 3	-	PASS
3	add function returns 5	Function returns the sum of inputs	-	PASS
4	test_add_two_numbers asserts result == 5	Test compares actual result with expected value 5	assertEqual(result, 5)	PASS
5	Test runner reports test_add_two_numbers PASSED	Test completed successfully	-	PASS

Failure Scenario

Failing Condition: If the add function returns incorrect result, e.g., returns a - b instead of a + b

Execution Trace Quiz - 3 Questions

What is the first step in Test-driven development (TDD) shown in this test?

A Run the program without tests

B Write the test before implementing the function

C Implement the function before writing the test

D Refactor the code without tests

Key Result

In TDD, writing the test first helps clarify requirements and ensures the code meets expectations before implementation.