GUI testing wiki

FSM (finite-state machine)

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Definition

A Finite State Machine is a model of computation, based on a hypothetical machine made of one or more states.

  • only one single state of this machine can be active at the same time
  • the machine has to transition from one state to another in to perform different actions

A Finite State Machine is any device storing the state of something at a given time. The state will change based on inputs, providing the resulting output for the implemented changes.

A FSM is characterized as follows:

  • We have a fixed set of states that the machine can be in
  • The machine can only be in one state at a time
  • A sequence of inputs is sent to the machine
  • Every state has a set of transitions and every transition is associated with an input and pointing to a state
 
const machine = {
    state: 'OFF',
    transitions: {
        OFF: {
            press() {
                this.state = 'ON'
            }
        },
        ON: {
            press() {
                this.state = 'BLINK';
            },
        },
        BLINK: {
            press() {
                this.state = 'OFF';
            },
        },
    },
    dispatch(actionName) {
        const action = this.transitions[this.state][actionName];
 
        if (action) {
            action.call(this);
        } else {
            console.log('invalid action');
        }
    },
};
 
const flashlight = Object.create(machine);
 
console.log(flashlight.state); // OFF
flashlight.dispatch('press'); 
console.log(flashlight.state); // ON
flashlight.dispatch('press');
console.log(flashlight.state); // BLINK

References

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