ITPEC FE Subject A October 2025 Question 36

A method that checks the system behaves as designed for each combination of event and internal state — that is the definition of a state transition test.

Test cases come from a state transition diagram or table. For every state, each event is applied and the test checks the resulting state and output, covering valid transitions and events that should be rejected in a given state. It suits systems whose behaviour depends on their current state, such as login flows or vending machines.

Answer (b)

Why not others:

• •(a) — a state transition test is a black box technique, but its whole point is the system's internal states.
• •(c) — systems whose state never changes with events are the opposite of what this method targets.
• •(d) — data flow diagrams model data movement and decision tables model condition combinations; the test is built from a state transition diagram or table.

Key rule: Choose the test design technique by the system's nature: state transition testing for state-dependent behaviour, decision tables for combinations of conditions.

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