From d7fac9c3d07147af83da2ca059e10942bb1bbd18 Mon Sep 17 00:00:00 2001
From: Sven van Heugten <sven@memcmp.org>
Date: Thu, 8 Jan 2026 21:45:46 +0100
Subject: [PATCH] Verify that non-remotely controlled lights are on if they
 have power

---
 .../InteractionListGenerators.fs                 |  4 ++--
 NightLight.Core.Tests/LightArbitraries.fs        |  7 +++++++
 NightLight.Core.Tests/NightLightTests.fs         | 16 ++++++++++++----
 3 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/NightLight.Core.Tests/InteractionListGenerators.fs b/NightLight.Core.Tests/InteractionListGenerators.fs
index e254b1a..641d87c 100644
--- a/NightLight.Core.Tests/InteractionListGenerators.fs
+++ b/NightLight.Core.Tests/InteractionListGenerators.fs
@@ -19,14 +19,14 @@ let private genHumanInteraction biasTowardsLight =
 let private genInteraction biasTowardsLight =
     Gen.oneof [ genTimeChanged; genHumanInteraction biasTowardsLight ]
 
-let private genInteractionsListThatStartsWithTimeChanged biasTowardsLight =
+let genInitialInteractions biasTowardsLight =
     [ genTimeChanged |> Gen.map List.singleton
       Gen.listOf <| genInteraction biasTowardsLight ]
     |> concatGens
 
 let genInitialInteractionsAndEndWith biasTowardsLight (endsWith: Interaction) =
     let genNonTrivialList =
-        genInteractionsListThatStartsWithTimeChanged biasTowardsLight
+        genInitialInteractions biasTowardsLight
         |> Gen.map (fun lst -> lst @ [ endsWith ])
 
     match endsWith with
diff --git a/NightLight.Core.Tests/LightArbitraries.fs b/NightLight.Core.Tests/LightArbitraries.fs
index 65240f6..e91e114 100644
--- a/NightLight.Core.Tests/LightArbitraries.fs
+++ b/NightLight.Core.Tests/LightArbitraries.fs
@@ -6,6 +6,13 @@ open FsCheck.FSharp
 type ArbitraryLight =
     static member Light() = lights |> Gen.elements |> Arb.fromGen
 
+type ArbitraryNonRemotelyControlledLight =
+    static member Light() =
+        lights
+        |> Seq.filter (not << _.ControlledWithRemote)
+        |> Gen.elements
+        |> Arb.fromGen
+
 type ArbitraryRemotelyControlledLight =
     static member Light() =
         lights |> Seq.filter _.ControlledWithRemote |> Gen.elements |> Arb.fromGen
diff --git a/NightLight.Core.Tests/NightLightTests.fs b/NightLight.Core.Tests/NightLightTests.fs
index 2eea0ea..4e795da 100644
--- a/NightLight.Core.Tests/NightLightTests.fs
+++ b/NightLight.Core.Tests/NightLightTests.fs
@@ -63,8 +63,16 @@ type NightLightTests() =
                 | Off -> true
                 | On(_, color) -> color = Red)
 
-    [<Property(Arbitrary = [| typeof<ArbitraryLight> |])>]
-    let ``After pressing 'On' on the remote, all lights with power should be on, as long as the 'Off' button isn't pressed``
+    [<Property(Arbitrary = [| typeof<ArbitraryNonRemotelyControlledLight> |])>]
+    let ``All non-remotely controlled lights should be on *if and only if* they have power`` (light: Light) =
+        genInitialInteractions light |> Arb.fromGen |> Prop.forAll
+        <| fun interactions ->
+            let fakeHome = createFakeHomeWithNightLightAndInteract interactions
+
+            doesLightHavePowerAfter light interactions = fakeHome.LightShouldHaveState light _.IsOn
+
+    [<Property(Arbitrary = [| typeof<ArbitraryRemotelyControlledLight> |])>]
+    let ``After pressing 'On' on the remote, all remotely controlled lights with power should be on, as long as the 'Off' button isn't pressed``
         (light: Light)
         =
         concatGens
@@ -78,8 +86,8 @@ type NightLightTests() =
             doesLightHavePowerAfter light interactions
             ==> fakeHome.LightShouldHaveState light _.IsOn
 
-    [<Property(Arbitrary = [| typeof<ArbitraryLight> |])>]
-    let ``After a new day starts, all lights with power should be on, as long as the 'Off' button isn't pressed``
+    [<Property(Arbitrary = [| typeof<ArbitraryRemotelyControlledLight> |])>]
+    let ``After a new day starts, all remotely controlled lights with power should be on, as long as the 'Off' button isn't pressed``
         (light: Light)
         =
         concatGens