Fix double subscription bug

Sources/Automaton.swift

@@ -78,7 +78,7 @@ public final class Automaton<State, Input>
                     .map { input, fromState in
                         return (input, fromState, mapping(fromState, input)?.1)
                     }
-                    .share(replay: 1)
+                    .share(replay: 1, scope: .forever)
 
                 let successSignal = mappingSignal
                     .filterMap { input, fromState, effect in
@@ -110,7 +110,7 @@ public final class Automaton<State, Input>
                     return .just(.failure(input, fromState))
                 }
             }
-            .share(replay: 1)
+            .share(replay: 1, scope: .forever)
 
         replySignal
             .flatMap(.merge) { reply -> Observable<State> in

Tests/RxAutomatonTests/EffectMappingSpec.swift

@@ -94,7 +94,32 @@ class EffectMappingSpec: QuickSpec
             }
 
         }
-
+
+        describe("Edge Invocation") {
+            var subscriptionsCount = 0
+
+            beforeEach {
+                subscriptionsCount = 0
+
+                // To reproduce the bug we need a plain cold observable
+                let loginOKProducer = Observable.just(AuthInput.loginOK)
+                    .do(onSubscribe: { subscriptionsCount += 1 })
+
+                let mappings: [Automaton.EffectMapping] = [
+                    .login    | .loggedOut  => .loggingIn  | loginOKProducer
+                ]
+
+                automaton = Automaton(state: .loggedOut, input: signal, mapping: reduce(mappings), strategy: .merge)
+            }
+
+            describe("loggedOut  => .loggingIn") {
+                it("subscribes to testableLoginOKProducer only once") {
+                    observer.onNext(.login)
+                    expect(subscriptionsCount) == 1
+                }
+            }
+        }
+
         describe("Func-based EffectMapping") {
 
             beforeEach {