Remove Time on FakeHome

We'll have a lot more stuff that we need to compute from the actual
interactions, so let's just get the boilerplate ready.

NightLight.Core.Tests/FakeHome.fs

@@ -44,8 +44,6 @@ type FakeLight(light: Light) =
             color <- newColor
 
 type FakeHome(now: DateTime) =
-    let mutable time = now
-
     let mutable nightLightStateMachine = NightLightStateMachine now
 
     let assertIsOkAndGet result =
@@ -95,8 +93,6 @@ type FakeHome(now: DateTime) =
         commands |> Seq.iter processCommand
         nightLightStateMachine <- newState
 
-    member _.Time = time
-
     member _.LightStates = friendlyNameToFakeLight.Values |> Seq.map _.LightWithState
 
     member _.Interact(interaction: Interaction) =
@@ -113,9 +109,7 @@ type FakeHome(now: DateTime) =
             |> ReceivedZigbeeEvent
             |> sendEvent
         | HumanInteraction(LightTurnedOff light) -> friendlyNameToFakeLight[light.FriendlyName].TurnOff()
-        | TimeChanged newTime ->
-            time <- newTime
-            newTime |> Event.TimeChanged |> sendEvent
+        | TimeChanged newTime -> newTime |> Event.TimeChanged |> sendEvent
 
 type FakeHome with
     member this.Interact(interactions: Interaction seq) = interactions |> Seq.iter this.Interact
@@ -127,9 +121,3 @@ type FakeHome with
             | On(brightness, color) -> Some(light, brightness, color)
             | Off -> None)
         |> Seq.forall condition
-
-    member this.IsDay() =
-        this.Time.TimeOfDay >= TimeSpan.FromHours 5.5
-        && this.Time.TimeOfDay < TimeSpan.FromHours 20.5
-
-    member this.IsNight() = not (this.IsDay())

NightLight.Core.Tests/NightLightTests.fs

@@ -4,6 +4,26 @@ open System
 open FsCheck.Xunit
 open FsCheck.FSharp
 
+module InteractionsHelpers =
+    let getTimeAfter interactions =
+        interactions
+        |> Seq.choose (fun interaction ->
+            match interaction with
+            | TimeChanged time -> Some time
+            | _ -> None)
+        |> Seq.tryLast
+        |> function
+            | Some time -> time
+            | None -> failwith "Time wasn't changed"
+
+    let isDayAfter interactions =
+        let time = getTimeAfter interactions
+
+        time.TimeOfDay >= TimeSpan.FromHours 5.5
+        && time.TimeOfDay < TimeSpan.FromHours 20.5
+
+    let isNightAfter = not << isDayAfter
+
 [<Properties(Arbitrary = [| typeof<Arbitraries> |])>]
 type NightLightTests() =
     [<Property>]
@@ -17,7 +37,7 @@ type NightLightTests() =
         let fakeHome = FakeHome now
         fakeHome.Interact interactions
 
-        fakeHome.IsNight()
+        InteractionsHelpers.isNightAfter interactions
         ==> fakeHome.ForAllLightsThatAreOn(fun (_, _, color) -> color = Red)
 
     [<Property>]
@@ -25,5 +45,5 @@ type NightLightTests() =
         let fakeHome = FakeHome now
         fakeHome.Interact interactions
 
-        fakeHome.IsDay()
+        InteractionsHelpers.isDayAfter interactions
         ==> fakeHome.ForAllLightsThatAreOn(fun (_, _, color) -> color = White || color = Yellow)