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State Transition Testing

State Transition Testing is a test case design technique used to verify how a system behaves when it moves from one state to another, based on events or actions.

State transition testing answers: “Does the system behave correctly as it changes states?”

1. Definition

State Transition Testing is a test case design technique used to verify how a system behaves when it moves from one state to another, based on events or actions.

State transition testing answers: “Does the system behave correctly as it changes states?”

2. When to Use State Transition Testing

  • System behavior depends on previous actions
  • Workflow-based or lifecycle-based systems
  • Applications with statuses or modes

3. Key Concepts in State Transition Testing

  • State – A condition or mode of the system
  • Event – An action that causes a state change
  • Transition – Movement from one state to another
  • Initial State – Starting point
  • Final State – Ending point

4. How to Design State Transition Tests

  1. Identify all possible states
  2. Identify valid and invalid events
  3. Draw a state transition diagram
  4. Create test cases for:
  • Valid transitions
  • Invalid transitions

5. Real-Time Example

ATM Card States:

  • Inserted
  • Authenticated
  • Transaction In Progress
  • Completed
  • Blocked

Test transitions:

  • Valid PIN → Authenticated
  • Invalid PIN (3 times) → Blocked

6. State Transition Diagram (Conceptual)

Inserted → Authenticated → Transaction → Completed
  ↓
Invalid PIN → Blocked

7. State Transition Testing vs Decision Table Testing

Aspect State Transition Decision Table
Focus State changes Condition combinations
Best for Workflow systems Rule-based logic

8. Common Defects Found

  • Invalid transitions allowed
  • Missing state transitions
  • Incorrect final state
  • State not updated properly

9. Common Mistakes

  • Ignoring invalid transitions
  • Missing intermediate states
  • Not considering previous state impact

10. Interview-Ready Answers

Short answer:

State transition testing verifies system behavior as it moves between different states based on events.

Detailed answer:

State transition testing is used to validate systems where output depends on both current input and previous state, ensuring correct state changes.

11. Key Takeaway

State Transition Testing ensures workflow integrity and correct system behavior over time.