Test coverage metrics in Testing Fundamentals - Test Execution Trace

Test Overview

This test checks if the test coverage tool correctly measures the percentage of code lines executed during testing. It verifies that the coverage report matches the expected coverage value.

Test Code - unittest with coverage.py

Testing Fundamentals

import unittest
import coverage

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

class TestCalculator(unittest.TestCase):
    def test_add(self):
        calc = Calculator()
        self.assertEqual(calc.add(2, 3), 5)

if __name__ == '__main__':
    cov = coverage.Coverage()
    cov.start()
    unittest.main(exit=False)
    cov.stop()
    cov.save()
    analysis = cov.analysis('test_coverage_metrics.py')
    coverage_percent = analysis[4]
    print(f"Coverage: {coverage_percent:.2f}%")
    assert coverage_percent >= 50, "Coverage is less than 50%"

Execution Trace - 4 Steps

Step	Action	System State	Assertion	Result
1	Test starts and coverage measurement begins	Coverage tool initialized, test runner ready	-	PASS
2	Test runner executes test_add method of TestCalculator	Calculator instance created, add method called with (2,3)	Check if add(2,3) returns 5	PASS
3	Coverage measurement stops and data saved	Coverage data collected for executed lines	-	PASS
4	Coverage report generated and coverage percentage calculated	Coverage report shows lines executed vs total lines	Assert coverage_percent >= 50	PASS

Failure Scenario

Failing Condition: Test coverage is below 50% because some code lines are not executed

Execution Trace Quiz - 3 Questions

What does the coverage tool measure in this test?

A The time taken to run the tests

B The percentage of code lines executed during the test

C The number of tests passed

D The number of errors in the code

Key Result

Always write tests that cover important code paths to ensure high test coverage and catch potential bugs early.