State transition testing in Testing Fundamentals - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding State Transition Diagrams

Which statement best describes the purpose of a state transition diagram in software testing?

A It shows how the system moves between different states based on events or inputs.

B It lists all the functions and methods in the software code.

C It displays the user interface layout and design elements.

D It records the performance metrics of the software during execution.

💡 Hint

Think about how software behaves differently depending on user actions or system events.

A state transition diagram visually represents the states of a system and how it changes from one state to another when events occur. This helps testers understand possible behaviors and test transitions.

❓ Predict Output

intermediate

Output of State Transition Test Simulation

Given the following simple state machine code simulation, what will be the final state after processing the events?

Testing Fundamentals

class StateMachine:
    def __init__(self):
        self.state = 'Locked'
    def on_event(self, event):
        if self.state == 'Locked' and event == 'coin':
            self.state = 'Unlocked'
        elif self.state == 'Unlocked' and event == 'push':
            self.state = 'Locked'
        return self.state

machine = StateMachine()
events = ['coin', 'push', 'push', 'coin', 'coin']
for e in events:
    machine.on_event(e)
print(machine.state)

A "Open"

B "Locked"

C "Error"

D "Unlocked"

💡 Hint

Trace the state changes step by step for each event.

The machine starts Locked. 'coin' unlocks it, 'push' locks it again. The sequence ends with the state 'Unlocked'.

❓ assertion

advanced

Correct Assertion for State Transition Test

Which assertion correctly verifies that a state machine transitions from 'Idle' to 'Processing' after receiving a 'start' event?

Testing Fundamentals

state_machine = StateMachine()
state_machine.state = 'Idle'
state_machine.on_event('start')

A assert state_machine.state != 'Processing'

B assert state_machine.state == 'Idle'

C assert state_machine.state == 'Processing'

D assert state_machine.state == 'Completed'

💡 Hint

Check the expected state after the 'start' event.

The assertion must confirm the state changed to 'Processing' after the event.

🔧 Debug

advanced

Identify the Bug in State Transition Code

What is the bug in the following state transition code snippet?

Testing Fundamentals

class Door:
    def __init__(self):
        self.state = 'Closed'
    def on_event(self, event):
        if self.state == 'Closed' and event == 'open':
            self.state = 'Open'
        elif self.state == 'Open' and event == 'close':
            self.state = 'Closed'
        elif event == 'lock':
            self.state = 'Locked'
        return self.state

A The 'lock' event can change state from any state, which may be invalid.

B The 'open' event is missing a condition to check if the door is already open.

C The constructor does not initialize the state variable.

D The method on_event does not return the new state.

💡 Hint

Consider if locking the door is allowed from all states.

The 'lock' event changes the state to 'Locked' regardless of the current state, which may allow locking an open door, which is usually invalid.

❓ framework

expert

Designing State Transition Test Cases

You are testing a vending machine with states: 'Idle', 'HasMoney', 'Dispensing', and 'OutOfStock'. Which set of test cases best covers all valid state transitions?

A Test only inserting money and selecting item, ignoring dispensing and out of stock states.

B Test inserting money from 'Idle', selecting item from 'HasMoney', dispensing item from 'Dispensing', and restocking from 'OutOfStock'.

C Test dispensing item directly from 'Idle' state without inserting money.

D Test restocking only when machine is 'Idle' and ignore other states.

💡 Hint

Think about covering all states and transitions between them.

Comprehensive testing requires covering all states and their valid transitions to ensure the machine behaves correctly in all scenarios.