Groovy for Domain-specific Languages - Second Edition

Chapter 8

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ledSwitch.switchOn()

then:

ledSwitch.state == 'ON'

when:

ledSwitch.switchOn()

then:

ledSwitch.state == 'ON'

when:

ledSwitch.switchOff()

then:

ledSwitch.state == 'OFF'

when:

ledSwitch.switchOff()

then:

ledSwitch.state == 'OFF'

Both these state machines use just two states. What if we have a more complex
state machine with multiple states, events, and transitions? The following is a state
machine that mimics the operation of an old cassette type tape machine:

state: "EMPTY"

state: "LOADED"

state: "RUNNING"

state: "PAUSED"

event: "load"

when: "EMPTY"

next = "LOADED"

event: "start"

when: "LOADED"

next = "RUNNING"

when: "PAUSED"

next = "RUNNING"

event: "pause"

when: "RUNNING"

next = "PAUSED"

event: "stop"

when: "RUNNING"

next = "LOADED"