State transition testing in Testing Fundamentals - Test Execution Trace

Test Overview

This test checks if a simple login system correctly changes states from 'Logged Out' to 'Logged In' and back to 'Logged Out' after logout. It verifies that the system allows login with correct credentials and denies access otherwise.

Test Code - unittest

Testing Fundamentals

class LoginSystem:
    def __init__(self):
        self.state = 'Logged Out'

    def login(self, username, password):
        if username == 'user' and password == 'pass':
            self.state = 'Logged In'
            return True
        else:
            return False

    def logout(self):
        if self.state == 'Logged In':
            self.state = 'Logged Out'
            return True
        return False

import unittest

class TestLoginSystem(unittest.TestCase):
    def setUp(self):
        self.system = LoginSystem()

    def test_valid_login_and_logout(self):
        # Initial state should be Logged Out
        self.assertEqual(self.system.state, 'Logged Out')

        # Login with correct credentials
        login_result = self.system.login('user', 'pass')
        self.assertTrue(login_result)
        self.assertEqual(self.system.state, 'Logged In')

        # Logout should return to Logged Out
        logout_result = self.system.logout()
        self.assertTrue(logout_result)
        self.assertEqual(self.system.state, 'Logged Out')

    def test_invalid_login(self):
        # Attempt login with wrong password
        login_result = self.system.login('user', 'wrong')
        self.assertFalse(login_result)
        self.assertEqual(self.system.state, 'Logged Out')

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

Execution Trace - 4 Steps

Step	Action	System State	Assertion	Result
1	Test starts and LoginSystem instance is created	System state is 'Logged Out'	Assert initial state is 'Logged Out'	PASS
2	Call login with username 'user' and password 'pass'	System processes login credentials	Assert login returns True and state changes to 'Logged In'	PASS
3	Call logout method	System processes logout	Assert logout returns True and state changes to 'Logged Out'	PASS
4	Call login with username 'user' and wrong password 'wrong'	System processes login credentials	Assert login returns False and state remains 'Logged Out'	PASS

Failure Scenario

Failing Condition: Login method does not change state to 'Logged In' on correct credentials

Execution Trace Quiz - 3 Questions

What is the initial state of the system before any action?

A Logged Out

B Logged In

C Unknown

D Error

Key Result

State transition testing verifies that the system correctly changes from one state to another based on inputs, ensuring all valid and invalid transitions behave as expected.