Exemplo n.º 1
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        public void CustomTypesForStatesAndEvents(
            AsyncPassiveStateMachine <MyState, MyEvent> machine,
            bool arrivedInStateB)
        {
            "establish a state machine with custom types for states and events"._(async() =>
            {
                machine = new AsyncPassiveStateMachine <MyState, MyEvent>();

                machine.In(new MyState("A"))
                .On(new MyEvent(1)).Goto(new MyState("B"));

                machine.In(new MyState("B"))
                .ExecuteOnEntry(() => arrivedInStateB = true);

                await machine.Initialize(new MyState("A"));

                await machine.Start();
            });

            "when using the state machine"._(() =>
                                             machine.Fire(new MyEvent(1)));

            "it should use equals to compare states and events"._(() =>
                                                                  arrivedInStateB.Should().BeTrue("state B should be current state"));
        }
Exemplo n.º 2
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        public void EventArgument(
            AsyncPassiveStateMachine <int, int> machine,
            int passedArgument)
        {
            const int argument = 17;

            "establish a state machine with an exit action taking an event argument".x(() =>
            {
                machine = new AsyncPassiveStateMachine <int, int>();

                machine.In(State)
                .ExecuteOnExit((int a) => passedArgument = a)
                .On(Event).Goto(AnotherState);

                machine.In(AnotherState)
                .ExecuteOnEntry((int a) => passedArgument = a);
            });

            "when leaving the state".x(async() =>
            {
                await machine.Initialize(State);
                await machine.Start();
                await machine.Fire(Event, argument);
            });

            "it should pass event argument to exit action".x(() =>
                                                             passedArgument.Should().Be(argument));
        }
        public void EventsQueueing(
            IAsyncStateMachine <string, int> machine)
        {
            const int firstEvent  = 0;
            const int secondEvent = 1;

            bool arrived = false;

            "establish a passive state machine with transitions".x(() =>
            {
                machine = new AsyncPassiveStateMachine <string, int>();

                machine.In("A").On(firstEvent).Goto("B");
                machine.In("B").On(secondEvent).Goto("C");
                machine.In("C").ExecuteOnEntry(() => arrived = true);

                machine.Initialize("A");
            });

            "when firing an event onto the state machine".x(() =>
            {
                machine.Fire(firstEvent);
                machine.Fire(secondEvent);
                machine.Start();
            });

            "it should queue event at the end".x(()
                                                 => arrived.Should().BeTrue("state machine should arrive at destination state"));
        }
Exemplo n.º 4
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        public void CommonAncestor(
            AsyncPassiveStateMachine <int, int> machine)
        {
            const int commonAncestorState       = 0;
            const int sourceState               = 1;
            const int parentOfSourceState       = 2;
            const int siblingOfSourceState      = 3;
            const int destinationState          = 4;
            const int parentOfDestinationState  = 5;
            const int siblingOfDestinationState = 6;
            const int Event = 0;

            bool commonAncestorStateLeft = false;

            "establish a hierarchical state machine"._(async() =>
            {
                machine = new AsyncPassiveStateMachine <int, int>();

                machine.DefineHierarchyOn(commonAncestorState)
                .WithHistoryType(HistoryType.None)
                .WithInitialSubState(parentOfSourceState)
                .WithSubState(parentOfDestinationState);

                machine.DefineHierarchyOn(parentOfSourceState)
                .WithHistoryType(HistoryType.None)
                .WithInitialSubState(sourceState)
                .WithSubState(siblingOfSourceState);

                machine.DefineHierarchyOn(parentOfDestinationState)
                .WithHistoryType(HistoryType.None)
                .WithInitialSubState(destinationState)
                .WithSubState(siblingOfDestinationState);

                machine.In(sourceState)
                .On(Event).Goto(destinationState);

                machine.In(commonAncestorState)
                .ExecuteOnExit(() => commonAncestorStateLeft = true);

                await machine.Initialize(sourceState);
                await machine.Start();
            });

            "when firing an event resulting in a transition with a common ancestor"._(()
                                                                                      => machine.Fire(Event));

            "the state machine should remain inside common ancestor state"._(()
                                                                             => commonAncestorStateLeft
                                                                             .Should().BeFalse());
        }
Exemplo n.º 5
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        public void ExitAction(
            AsyncPassiveStateMachine <int, int> machine,
            bool exitActionExecuted,
            bool asyncExitActionExecuted)
        {
            "establish a state machine with exit action on a state".x(() =>
            {
                machine = new AsyncPassiveStateMachine <int, int>();

                machine.In(State)
                .ExecuteOnExit(() => exitActionExecuted = true)
                .ExecuteOnExit(async() =>
                {
                    asyncExitActionExecuted = true;
                    await Task.Yield();
                })
                .On(Event).Goto(AnotherState);
            });

            "when leaving the state".x(async() =>
            {
                await machine.Initialize(State);
                await machine.Start();
                await machine.Fire(Event);
            });

            "it should execute the synchronous exit action".x(()
                                                              => exitActionExecuted.Should().BeTrue());

            "it should execute the asynchronous exit action".x(()
                                                               => asyncExitActionExecuted.Should().BeTrue());
        }
Exemplo n.º 6
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        public void OtherwiseGuard(
            AsyncPassiveStateMachine <int, int> machine,
            CurrentStateExtension currentStateExtension)
        {
            "establish a state machine with otherwise guard and no machting other guard".x(async() =>
            {
                machine = new AsyncPassiveStateMachine <int, int>();

                currentStateExtension = new CurrentStateExtension();
                machine.AddExtension(currentStateExtension);

                machine.In(SourceState)
                .On(Event)
                .If(() => Task.FromResult(false)).Goto(ErrorState)
                .Otherwise().Goto(DestinationState);

                await machine.Initialize(SourceState);
                await machine.Start();
            });

            "when an event is fired".x(()
                                       => machine.Fire(Event));

            "it should_take_transition_guarded_with_otherwise".x(()
                                                                 => currentStateExtension.CurrentState.Should().Be(DestinationState));
        }
Exemplo n.º 7
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        public void NoMatchingGuard(
            AsyncPassiveStateMachine <int, int> machine)
        {
            bool declined = false;

            "establish state machine with no matching guard".x(async() =>
            {
                machine = new AsyncPassiveStateMachine <int, int>();

                var currentStateExtension = new CurrentStateExtension();
                machine.AddExtension(currentStateExtension);

                machine.In(SourceState)
                .On(Event)
                .If(() => Task.FromResult(false)).Goto(ErrorState);

                machine.TransitionDeclined += (sender, e) => declined = true;

                await machine.Initialize(SourceState);
                await machine.Start();
            });

            "when an event is fired".x(()
                                       => machine.Fire(Event));

            "it should notify about declined transition".x(()
                                                           => declined.Should().BeTrue("TransitionDeclined event should be fired"));
        }
Exemplo n.º 8
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        public void MatchingGuard(
            AsyncPassiveStateMachine <int, int> machine,
            CurrentStateExtension currentStateExtension)
        {
            "establish a state machine with guarded transitions".x(async() =>
            {
                machine = new AsyncPassiveStateMachine <int, int>();

                currentStateExtension = new CurrentStateExtension();
                machine.AddExtension(currentStateExtension);

                machine.In(SourceState)
                .On(Event)
                .If(() => false).Goto(ErrorState)
                .If(async() => await Task.FromResult(false)).Goto(ErrorState)
                .If(async() => await Task.FromResult(true)).Goto(DestinationState)
                .If(() => true).Goto(ErrorState)
                .Otherwise().Goto(ErrorState);

                await machine.Initialize(SourceState);
                await machine.Start();
            });

            "when an event is fired".x(()
                                       => machine.Fire(Event));

            "it should take transition guarded with first matching guard".x(()
                                                                            => currentStateExtension.CurrentState.Should().Be(DestinationState));
        }
Exemplo n.º 9
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        public void EntryAction(
            AsyncPassiveStateMachine <int, int> machine,
            bool entryActionExecuted,
            bool asyncEntryActionExecuted)
        {
            "establish a state machine with entry action on a state".x(() =>
            {
                machine = new AsyncPassiveStateMachine <int, int>();

                machine.In(State)
                .ExecuteOnEntry(() => entryActionExecuted = true)
                .ExecuteOnEntry(async() =>
                {
                    asyncEntryActionExecuted = true;
                    await Task.Yield();
                });
            });

            "when entering the state".x(async() =>
            {
                await machine.Initialize(State);
                await machine.Start();
            });

            "it should execute the synchronous entry action".x(()
                                                               => entryActionExecuted.Should().BeTrue());

            "it should execute the asynchronous entry action".x(()
                                                                => asyncEntryActionExecuted.Should().BeTrue());
        }
Exemplo n.º 10
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        public void BeforeExecutingEntryActions(
            AsyncPassiveStateMachine<string, int> machine,
            IExtension<string, int> extension)
        {
            "establish an extension".x(()
                => extension = A.Fake<IExtension<string, int>>());

            "establish a state machine using the extension".x(async () =>
            {
                machine = new AsyncPassiveStateMachine<string, int>(Name);

                machine.AddExtension(extension);

                machine.In("0")
                    .On(1).Goto("1");

                await machine.Initialize("0");
                await machine.Start();
            });

            "when firing an event onto the state machine".x(()
                => machine.Fire(1));

            "it should call EnteringState on registered extensions for target state".x(()
                => A.CallTo(() => extension.EnteringState(
                        A<IStateMachineInformation<string, int>>.That.Matches(x => x.Name == Name && x.CurrentStateId == "1"),
                        A<IState<string, int>>.That.Matches(x => x.Id == "1"),
                        A<ITransitionContext<string, int>>.That.Matches(x => x.EventId.Value == 1)))
                    .MustHaveHappened());
        }
Exemplo n.º 11
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        public void Start(
            AsyncPassiveStateMachine <int, int> machine,
            bool entryActionExecuted)
        {
            "establish an initialized state machine".x(() =>
            {
                machine = new AsyncPassiveStateMachine <int, int>();

                machine.AddExtension(this.testExtension);

                machine.In(TestState)
                .ExecuteOnEntry(() => entryActionExecuted = true);

                machine.Initialize(TestState);
            });

            "when starting the state machine".x(() =>
                                                machine.Start());

            "should set current state of state machine to state to which it is initialized".x(() =>
                                                                                              this.testExtension.CurrentState.Should().Be(TestState));

            "should execute entry action of state to which state machine is initialized".x(() =>
                                                                                           entryActionExecuted.Should().BeTrue());
        }
Exemplo n.º 12
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        public void ExceptionHandling(
            AsyncPassiveStateMachine <int, int> machine,
            bool exitAction1Executed,
            bool exitAction2Executed,
            bool exitAction3Executed,
            bool exitAction4Executed)
        {
            var exception2        = new Exception();
            var exception3        = new Exception();
            var exception4        = new Exception();
            var receivedException = new List <Exception>();

            "establish a state machine with several exit actions on a state and some of them throw an exception".x(() =>
            {
                machine = new AsyncPassiveStateMachine <int, int>();

                machine.In(State)
                .ExecuteOnExit(() => exitAction1Executed = true)
                .ExecuteOnExit(() =>
                {
                    exitAction2Executed = true;
                    throw exception2;
                })
                .ExecuteOnExit(() =>
                {
                    exitAction3Executed = true;
                    throw exception3;
                })
                .ExecuteOnExit(async() =>
                {
                    exitAction4Executed = true;
                    await Task.Yield();
                    throw exception4;
                })
                .On(Event).Goto(AnotherState);

                machine.TransitionExceptionThrown += (s, e) => receivedException.Add(e.Exception);
            });

            "when entering the state".x(async() =>
            {
                await machine.Initialize(State);
                await machine.Start();
                await machine.Fire(Event);
            });

            "it should execute all entry actions on entry".x(()
                                                             => new[]
            {
                exitAction1Executed,
                exitAction2Executed,
                exitAction3Executed,
                exitAction4Executed
            }.Should().Equal(true, true, true, true));

            "it should handle all exceptions of all throwing entry actions by firing the TransitionExceptionThrown event".x(() =>
                                                                                                                            receivedException
                                                                                                                            .Should().BeEquivalentTo(exception2, exception3, exception4));
        }
        public void CustomFactory(
            StandardFactory <string, int> factory)
        {
            "establish a custom factory".x(()
                                           => factory = A.Fake <StandardFactory <string, int> >());

            "when creating a passive state machine".x(() =>
            {
                var machine = new AsyncPassiveStateMachine <string, int>("_", factory);

                machine.In("initial").On(42).Goto("answer");
            });

            "it should use custom factory to create internal instances".x(()
                                                                          => A.CallTo(factory).MustHaveHappened());
        }
Exemplo n.º 14
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        public void MultipleExitActions(
            AsyncPassiveStateMachine <int, int> machine,
            bool exitAction1Executed,
            bool exitAction2Executed,
            bool asyncExitAction1Executed,
            bool asyncExitAction2Executed)
        {
            "establish a state machine with several exit actions on a state".x(() =>
            {
                machine = new AsyncPassiveStateMachine <int, int>();

                machine.In(State)
                .ExecuteOnExit(() => exitAction1Executed = true)
                .ExecuteOnExit(() => exitAction2Executed = true)
                .ExecuteOnExit(async() =>
                {
                    asyncExitAction1Executed = true;
                    await Task.Yield();
                })
                .ExecuteOnExit(async() =>
                {
                    asyncExitAction2Executed = true;
                    await Task.Yield();
                })
                .On(Event).Goto(AnotherState);
            });

            "when leaving the state".x(async() =>
            {
                await machine.Initialize(State);
                await machine.Start();
                await machine.Fire(Event);
            });

            "it should execute all exit actions".x(()
                                                   => new[]
            {
                exitAction1Executed,
                exitAction2Executed,
                asyncExitAction1Executed,
                asyncExitAction2Executed
            }.Should().Equal(true, true, true, true));
        }
Exemplo n.º 15
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        public void ExitActionWithParameter(
            AsyncPassiveStateMachine <int, int> machine,
            string receivedParameter,
            string asyncReceivedParameter)
        {
            const string parameter = "parameter";

            "establish a state machine with exit action with parameter on a state".x(() =>
            {
                machine = new AsyncPassiveStateMachine <int, int>();

                machine.In(State)
                .ExecuteOnExitParametrized(p => receivedParameter = p, parameter)
                .ExecuteOnExitParametrized(
                    async p =>
                {
                    asyncReceivedParameter = p;
                    await Task.Yield();
                },
                    parameter)
                .On(Event).Goto(AnotherState);
            });

            "when leaving the state".x(async() =>
            {
                await machine.Initialize(State);
                await machine.Start();
                await machine.Fire(Event);
            });

            "it should execute the synchronous exit action".x(() =>
                                                              receivedParameter.Should().NotBeNull());

            "it should pass parameter to the synchronous exit action".x(() =>
                                                                        receivedParameter.Should().Be(parameter));

            "it should execute the asynchronous exit action".x(() =>
                                                               asyncReceivedParameter.Should().NotBeNull());

            "it should pass parameter to the asynchronous exit action".x(() =>
                                                                         asyncReceivedParameter.Should().Be(parameter));
        }
Exemplo n.º 16
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        public void Initialize(
            AsyncPassiveStateMachine <int, int> machine,
            bool entryActionExecuted)
        {
            "establish a state machine".x(() =>
            {
                machine = new AsyncPassiveStateMachine <int, int>();

                machine.AddExtension(this.testExtension);

                machine.In(TestState)
                .ExecuteOnEntry(() => entryActionExecuted = true);
            });

            "when state machine is initialized".x(() =>
                                                  machine.Initialize(TestState));

            "should not yet execute any entry actions".x(() =>
                                                         entryActionExecuted.Should().BeFalse());
        }
Exemplo n.º 17
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        public void BeforeExecutingEntryActionsHierarchical(
            AsyncPassiveStateMachine<string, string> machine,
            IExtension<string, string> extension)
        {
            "establish an extension".x(()
                => extension = A.Fake<IExtension<string, string>>());

            "establish a hierarchical state machine using the extension".x(async () =>
            {
                machine = new AsyncPassiveStateMachine<string, string>(Name);

                machine.AddExtension(extension);

                machine.DefineHierarchyOn("A")
                    .WithHistoryType(HistoryType.None)
                    .WithInitialSubState("A0");

                machine.In("0")
                    .On("A0").Goto("A0");

                await machine.Initialize("0");
                await machine.Start();
            });

            "when firing an event onto the state machine".x(()
                => machine.Fire("A0"));

            "it should call EnteringState on registered extensions for entered super states of target state".x(()
                => A.CallTo(() => extension.EnteringState(
                        A<IStateMachineInformation<string, string>>.That.Matches(x => x.Name == Name && x.CurrentStateId == "A0"),
                        A<IState<string, string>>.That.Matches(x => x.Id == "A"),
                        A<ITransitionContext<string, string>>.That.Matches(x => x.EventId.Value == "A0")))
                    .MustHaveHappened());

            "it should call EnteringState on registered extensions for entered leaf target state".x(()
                => A.CallTo(() => extension.EnteringState(
                        A<IStateMachineInformation<string, string>>.That.Matches(x => x.Name == Name && x.CurrentStateId == "A0"),
                        A<IState<string, string>>.That.Matches(x => x.Id == "A0"),
                        A<ITransitionContext<string, string>>.That.Matches(x => x.EventId.Value == "A0")))
                    .MustHaveHappened());
        }
Exemplo n.º 18
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        public void MultipleEntryActions(
            AsyncPassiveStateMachine <int, int> machine,
            bool entryAction1Executed,
            bool asyncEntryAction1Executed,
            bool entryAction2Executed,
            bool asyncEntryAction2Executed)
        {
            "establish a state machine with several entry actions on a state".x(() =>
            {
                machine = new AsyncPassiveStateMachine <int, int>();

                machine.In(State)
                .ExecuteOnEntry(() => entryAction1Executed = true)
                .ExecuteOnEntry(async() =>
                {
                    asyncEntryAction1Executed = true;
                    await Task.Yield();
                })
                .ExecuteOnEntry(() => entryAction2Executed = true)
                .ExecuteOnEntry(async() =>
                {
                    asyncEntryAction2Executed = true;
                    await Task.Yield();
                });
            });

            "when entering the state".x(async() =>
            {
                await machine.Initialize(State);
                await machine.Start();
            });

            "it should execute all entry actions".x(()
                                                    => new[]
            {
                entryAction1Executed,
                asyncEntryAction1Executed,
                entryAction2Executed,
                asyncEntryAction2Executed
            }.Should().Equal(true, true, true, true));
        }
Exemplo n.º 19
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        public void EntryActionWithParameter(
            AsyncPassiveStateMachine <int, int> machine,
            string receivedParameter,
            string asyncReceivedParameter)
        {
            const string parameter = "parameter";

            "establish a state machine with entry action with parameter on a state"._(() =>
            {
                machine = new AsyncPassiveStateMachine <int, int>();

                machine.In(State)
                .ExecuteOnEntryParametrized(p => receivedParameter = p, parameter)
                .ExecuteOnEntryParametrized(
                    async p =>
                {
                    asyncReceivedParameter = p;
                    await Task.Yield();
                },
                    parameter);
            });

            "when entering the state"._(async() =>
            {
                await machine.Initialize(State);
                await machine.Start();
            });

            "it should execute the entry synchronous action"._(()
                                                               => receivedParameter.Should().NotBeNull());

            "it should pass parameter to the synchronous entry action"._(()
                                                                         => receivedParameter.Should().Be(parameter));

            "it should execute the asynchronous entry action"._(()
                                                                => asyncReceivedParameter.Should().NotBeNull());

            "it should pass parameter to the asynchronous entry action"._(()
                                                                          => asyncReceivedParameter.Should().Be(parameter));
        }
Exemplo n.º 20
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        public GossipManager(GossipNode gossipNode)
        {
            _gossipNode            = gossipNode;
            _cts                   = new CancellationTokenSource();
            _currentStateExtension = new CurrentStateExtension();

            _requests       = new ConcurrentDictionary <string, BaseMessage>();
            _helloTimer     = new Timer(new TimerCallback(HelloTimerHandle));
            _heartbeatTimer = new Timer(new TimerCallback(HeartbeatTimerHandle));

            _fsm = new AsyncPassiveStateMachine <NodeState, GossipEvent>("GossipManager");
            _fsm.AddExtension(new ConsoleLogExtension());
            _fsm.AddExtension(_currentStateExtension);

            _fsm.Initialize(NodeState.Initialized);

            _fsm.In(NodeState.Initialized)
            .On(GossipEvent.HelloSend)
            .Goto(NodeState.HelloSent)
            .Execute(async() =>
            {
                // set hello timer
                await SendHello();
            });

            _fsm.In(NodeState.HelloSent)
            .On(GossipEvent.HelloAnswer)
            .Goto(NodeState.Infected)
            .Execute <HelloResponse>((msg) =>
            {
                ReceiveHelloAnswer(msg);
            })
            .On(GossipEvent.HelloExpired)
            .Goto(NodeState.Initialized)
            .Execute(async() =>
            {
                // hello timer re-set
                await SendHello();
            });

            _fsm.In(NodeState.Infected)
            .On(GossipEvent.HeartbeatExpired)
            .Goto(NodeState.Susceptible)
            .Execute(async() =>
            {
                await SendHeartbeat();
            })
            .On(GossipEvent.HeartbeatAnswer)
            .Goto(NodeState.Infected)
            .Execute <HeartbeatResponse>((msg) => {
                IGossipPeer senderPeer = msg.Members?.FirstOrDefault();
                MergeLists(senderPeer, msg.Members);
            });

            _fsm.In(NodeState.Infected)
            .On(GossipEvent.HelloReceive)
            .Execute <HelloRequest>(async(msg) =>
            {
                await SendHelloAnswer(msg);
            });

            _fsm.In(NodeState.Susceptible)
            .On(GossipEvent.HelloReceive)
            .Execute <HelloRequest>(async(msg) =>
            {
                await SendHelloAnswer(msg);
            })
            .On(GossipEvent.HeartbeatReceive)
            .If <HeartbeatRequest>((msg) =>
            {
                return(_gossipNode.GossipPeer.Heartbeat < msg.Peer.Heartbeat);
            })
            .Goto(NodeState.Infected)
            .Execute <HeartbeatRequest>(async(msg) =>
            {
                await ReceiveHeartbeat(msg);
            })
            .On(GossipEvent.HeartbeatAnswer)
            .If <HeartbeatResponse>((msg) =>
            {
                return(msg.Members[0].Heartbeat > _gossipNode.GossipPeer.Heartbeat);
            }).Goto(NodeState.Infected);

            _fsm.Start();
        }
Exemplo n.º 21
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        public void ExecutingTransition(
            AsyncPassiveStateMachine <int, int> machine,
            string actualParameter,
            string asyncActualParameter,
            bool exitActionExecuted,
            bool entryActionExecuted,
            bool asyncExitActionExecuted,
            bool asyncEntryActionExecuted)
        {
            "establish a state machine with transitions"._(async() =>
            {
                machine = new AsyncPassiveStateMachine <int, int>();

                machine.AddExtension(CurrentStateExtension);

                machine.In(SourceState)
                .ExecuteOnExit(() => exitActionExecuted = true)
                .ExecuteOnExit(async() =>
                {
                    asyncExitActionExecuted = true;
                    await Task.Yield();
                })
                .On(Event).Goto(DestinationState)
                .Execute((string p) => actualParameter = p)
                .Execute(async(string p) =>
                {
                    asyncActualParameter = p;
                    await Task.Yield();
                });

                machine.In(DestinationState)
                .ExecuteOnEntry(() => entryActionExecuted = true)
                .ExecuteOnEntry(async() =>
                {
                    asyncEntryActionExecuted = true;
                    await Task.Yield();
                });

                await machine.Initialize(SourceState);
                await machine.Start();
            });

            "when firing an event onto the state machine"._(()
                                                            => machine.Fire(Event, Parameter));

            "it should execute transition by switching state"._(()
                                                                => CurrentStateExtension.CurrentState.Should().Be(DestinationState));

            "it should execute synchronous transition actions"._(()
                                                                 => actualParameter.Should().NotBeNull());

            "it should execute asynchronous transition actions"._(()
                                                                  => asyncActualParameter.Should().NotBeNull());

            "it should pass parameters to transition action"._(()
                                                               => actualParameter.Should().Be(Parameter));

            "it should execute synchronous exit action of source state"._(()
                                                                          => exitActionExecuted.Should().BeTrue());

            "it should execute asynchronous exit action of source state"._(()
                                                                           => asyncExitActionExecuted.Should().BeTrue());

            "it should execute synchronous entry action of destination state"._(()
                                                                                => entryActionExecuted.Should().BeTrue());

            "it should execute asynchronous entry action of destination state"._(()
                                                                                 => asyncEntryActionExecuted.Should().BeTrue());
        }
Exemplo n.º 22
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        public void NoCommonAncestor(
            AsyncPassiveStateMachine <string, int> machine)
        {
            const string sourceState                   = "SourceState";
            const string parentOfSourceState           = "ParentOfSourceState";
            const string siblingOfSourceState          = "SiblingOfSourceState";
            const string destinationState              = "DestinationState";
            const string parentOfDestinationState      = "ParentOfDestinationState";
            const string siblingOfDestinationState     = "SiblingOfDestinationState";
            const string grandParentOfSourceState      = "GrandParentOfSourceState";
            const string grandParentOfDestinationState = "GrandParentOfDestinationState";
            const int    Event = 0;

            var log = string.Empty;

            "establish a hierarchical state machine"._(async() =>
            {
                machine = new AsyncPassiveStateMachine <string, int>();

                machine.DefineHierarchyOn(parentOfSourceState)
                .WithHistoryType(HistoryType.None)
                .WithInitialSubState(sourceState)
                .WithSubState(siblingOfSourceState);

                machine.DefineHierarchyOn(parentOfDestinationState)
                .WithHistoryType(HistoryType.None)
                .WithInitialSubState(destinationState)
                .WithSubState(siblingOfDestinationState);

                machine.DefineHierarchyOn(grandParentOfSourceState)
                .WithHistoryType(HistoryType.None)
                .WithInitialSubState(parentOfSourceState);

                machine.DefineHierarchyOn(grandParentOfDestinationState)
                .WithHistoryType(HistoryType.None)
                .WithInitialSubState(parentOfDestinationState);

                machine.In(sourceState)
                .ExecuteOnExit(() => log += "exit" + sourceState)
                .On(Event).Goto(destinationState);

                machine.In(parentOfSourceState)
                .ExecuteOnExit(() => log += "exit" + parentOfSourceState);

                machine.In(destinationState)
                .ExecuteOnEntry(() => log += "enter" + destinationState);

                machine.In(parentOfDestinationState)
                .ExecuteOnEntry(() => log += "enter" + parentOfDestinationState);

                machine.In(grandParentOfSourceState)
                .ExecuteOnExit(() => log += "exit" + grandParentOfSourceState);

                machine.In(grandParentOfDestinationState)
                .ExecuteOnEntry(() => log += "enter" + grandParentOfDestinationState);

                await machine.Initialize(sourceState);
                await machine.Start();
            });

            "when firing an event resulting in a transition without a common ancestor"._(()
                                                                                         => machine.Fire(Event));

            "it should execute exit action of source state"._(() =>
                                                              log.Should().Contain("exit" + sourceState));

            "it should execute exit action of parents of source state (recursively)"._(()
                                                                                       => log
                                                                                       .Should().Contain("exit" + parentOfSourceState)
                                                                                       .And.Contain("exit" + grandParentOfSourceState));

            "it should execute entry action of parents of destination state (recursively)"._(()
                                                                                             => log
                                                                                             .Should().Contain("enter" + parentOfDestinationState)
                                                                                             .And.Contain("enter" + grandParentOfDestinationState));

            "it should execute entry action of destination state"._(()
                                                                    => log.Should().Contain("enter" + destinationState));

            "it should execute actions from source upwards and then downwards to destination state"._(() =>
            {
                string[] states =
                {
                    sourceState,
                    parentOfSourceState,
                    grandParentOfSourceState,
                    grandParentOfDestinationState,
                    parentOfDestinationState,
                    destinationState
                };

                var statesInOrderOfAppearanceInLog = states
                                                     .OrderBy(s => log.IndexOf(s.ToString(CultureInfo.InvariantCulture), StringComparison.Ordinal));
                statesInOrderOfAppearanceInLog
                .Should().Equal(states);
            });
        }