State Transition Technique

State transition testing is used where some aspect of the system can be described in what is called a ‘finite state machine’.

Any system where you get a different output for the same input, depending on what has happened before, is a finite state system.

A finite state system is often shown as a state diagram

One of the advantages of the state transition technique is that the model can be as detailed or as abstract as you need it to be. Where a part of the system is more important (that is, requires more testing) a greater depth of detail can be modeled. Where the system is less important (requires less testing), the model can use a single state to signify what would otherwise be a series of different states.

A state transition model has four basic parts: State, Transition, Events and Actions.

 

 

Hence we can see that in any given state, one event can cause only one action, but that the same event – from a different state – may cause a different action and a different end state.

 

Test conditions can be derived from the state graph in various ways. Each state can be noted as a test condition, as can each transition.

 

Ref: http://istqbexamcertification.com/what-is-state-transition-testing-in-software-testing/