Replace the 'initial interactions' concept with ensureStartsWithTimeChanged

This allows us to generate the case again where the list *just* contains
a TimeChanged interaction.

NightLight.Core.Tests/InteractionListGenerators.fs

@@ -2,8 +2,8 @@ module NightLight.Core.Tests.InteractionListGenerators
 
 open FsCheck.FSharp
 open NightLight.Core.Models
-open NightLight.Core.Tests.GenHelpers
 open NightLight.Core.Tests.TimeChangedGenerators
+open FsCheck
 
 let private genHumanInteraction biasTowardsLight =
     let genLightInteraction =
@@ -19,17 +19,17 @@ let private genHumanInteraction biasTowardsLight =
 let private genInteraction biasTowardsLight =
     Gen.oneof [ genTimeChanged; genHumanInteraction biasTowardsLight ]
 
-let genInitialInteractions biasTowardsLight =
-    [ genTimeChanged |> Gen.map List.singleton
-      Gen.listOf <| genInteraction biasTowardsLight ]
-    |> concatGens
-
 let genRandomInteractionsExcept biasTowardsLight disqualifier =
     genInteraction biasTowardsLight
     |> Gen.filter (not << disqualifier)
     |> Gen.listOf
 
-let genInitialInteractionsExcept biasTowardsLight disqualifier =
+let genRandomInteractions biasTowardsLight =
-    [ genTimeChanged |> Gen.map List.singleton
+    genRandomInteractionsExcept biasTowardsLight (fun _ -> false)
-      genRandomInteractionsExcept biasTowardsLight disqualifier ]
+
-    |> concatGens
+let ensureStartsWithTimeChanged (genInteractions: Gen<Interaction list>) =
+    genInteractions
+    |> Gen.bind (fun interactions ->
+        match interactions with
+        | Interaction.TimeChanged _ :: _ -> Gen.constant interactions
+        | _ -> genTimeChanged |> Gen.map (fun tc -> tc :: interactions))

NightLight.Core.Tests/NightLightTests.fs

@@ -46,9 +46,10 @@ type NightLightTests() =
     [<Property(Arbitrary = [| typeof<ArbitraryLight> |])>]
     let ``All lights should be either off, white or yellow during the day`` (light: Light) =
         concatGens
-            [ genInitialInteractions light
+            [ genRandomInteractions light
               genTimeChangedToRandomDayTime |> Gen.map List.singleton
               genRandomInteractionsExcept light isTimeChangedToAnyNightTime ]
+        |> ensureStartsWithTimeChanged
         |> Arb.fromGen
         |> Prop.forAll
         <| fun interactions ->
@@ -61,9 +62,10 @@ type NightLightTests() =
     [<Property(Arbitrary = [| typeof<ArbitraryLight> |])>]
     let ``All lights should be either off or red during the night`` (light: Light) =
         concatGens
-            [ genInitialInteractions light
+            [ genRandomInteractions light
               genTimeChangedToRandomNightTime |> Gen.map List.singleton
               genRandomInteractionsExcept light isTimeChangedToAnyDayTime ]
+        |> ensureStartsWithTimeChanged
         |> Arb.fromGen
         |> Prop.forAll
         <| fun interactions ->
@@ -75,7 +77,10 @@ type NightLightTests() =
 
     [<Property(Arbitrary = [| typeof<ArbitraryNonRemotelyControlledLight> |])>]
     let ``All non-remotely controlled lights should be on iff they have power`` (light: Light) =
-        genInitialInteractions light |> Arb.fromGen |> Prop.forAll
+        genRandomInteractions light
+        |> ensureStartsWithTimeChanged
+        |> Arb.fromGen
+        |> Prop.forAll
         <| fun interactions ->
             let fakeHome = createFakeHomeWithNightLightAndInteract interactions
 
@@ -85,7 +90,8 @@ type NightLightTests() =
     let ``All remote controlled lights with power should be on if the 'Off' button on the remote was never pressed``
         (light: Light)
         =
-        genInitialInteractionsExcept light ((=) (HumanInteraction RemotePressedOffButton))
+        genRandomInteractionsExcept light ((=) (HumanInteraction RemotePressedOffButton))
+        |> ensureStartsWithTimeChanged
         |> Arb.fromGen
         |> Prop.forAll
         <| fun interactions ->
@@ -99,9 +105,10 @@ type NightLightTests() =
         (light: Light)
         =
         concatGens
-            [ genInitialInteractions light
+            [ genRandomInteractions light
               HumanInteraction RemotePressedOnButton |> List.singleton |> Gen.constant
               genRandomInteractionsExcept light ((=) (HumanInteraction RemotePressedOffButton)) ]
+        |> ensureStartsWithTimeChanged
         |> Arb.fromGen
         |> Prop.forAll
         <| fun interactions ->
@@ -115,11 +122,12 @@ type NightLightTests() =
         (light: Light)
         =
         concatGens
-            [ genInitialInteractions light
+            [ genRandomInteractions light
               genTimeChangedToRandomNightTime |> Gen.map List.singleton
               genRandomInteractionsExcept light isTimeChangedToAnyDayTime
               genTimeChangedToRandomDayTime |> Gen.map List.singleton
               genRandomInteractionsExcept light ((=) (HumanInteraction RemotePressedOffButton)) ]
+        |> ensureStartsWithTimeChanged
         |> Arb.fromGen
         |> Prop.forAll
         <| fun interactions ->
@@ -133,11 +141,12 @@ type NightLightTests() =
         (light: Light)
         =
         concatGens
-            [ genInitialInteractions light
+            [ genRandomInteractions light
               HumanInteraction RemotePressedOffButton |> List.singleton |> Gen.constant
               genRandomInteractionsExcept light (fun interaction ->
                   interaction = HumanInteraction RemotePressedOnButton
                   || interaction |> isTimeChangedToAnyDayTime) ]
+        |> ensureStartsWithTimeChanged
         |> Arb.fromGen
         |> Prop.forAll
         <| fun interactions ->