Bias the TimeChanged generator to make alarms more likely

NightLight.Core.Tests/InteractionListGenerators.fs

@@ -2,10 +2,33 @@ module NightLight.Core.Tests.InteractionListGenerators
 
 open System
 open NightLight.Core.Models
+open NightLight.Core.Tests.InteractionListHelpers
 open FsCheck.FSharp
 
 let private genTimeChanged =
-    ArbMap.defaults |> ArbMap.generate<DateTime> |> Gen.map Interaction.TimeChanged
+    let genDate = ArbMap.defaults |> ArbMap.generate<DateTime> |> Gen.map _.Date
+
+    let genTimeSpanBetween (l: TimeSpan) (h: TimeSpan) =
+        Gen.choose (int l.TotalSeconds, int h.TotalSeconds)
+        |> Gen.map int64
+        |> Gen.map TimeSpan.FromSeconds
+
+    let (+) = Gen.map2 (+)
+
+    let genDayBoundaryDateTime =
+        genDate
+        + Gen.elements [ startOfDay; endOfDay ]
+        + genTimeSpanBetween (-TimeSpan.FromMinutes 20.0) (TimeSpan.FromMinutes 20.0)
+
+    let genStartOfDayDateTime =
+        genDate
+        + Gen.constant startOfDay
+        + genTimeSpanBetween TimeSpan.Zero (TimeSpan.FromMinutes 20.0)
+
+    let genAnyDateTime = ArbMap.defaults |> ArbMap.generate<DateTime>
+
+    Gen.frequency [ 4, genStartOfDayDateTime; 2, genDayBoundaryDateTime; 1, genAnyDateTime ]
+    |> Gen.map Interaction.TimeChanged
 
 let private genHumanInteraction =
     Gen.elements lights

NightLight.Core.Tests/NightLight.Core.Tests.fsproj

@@ -9,8 +9,8 @@
     <ItemGroup>
         <Compile Include="FakeHome.fs" />
         <Compile Include="GenHelpers.fs" />
-        <Compile Include="InteractionListGenerators.fs" />
         <Compile Include="InteractionListHelpers.fs" />
+        <Compile Include="InteractionListGenerators.fs" />
         <Compile Include="LightArbitraries.fs" />
         <Compile Include="NightLightTests.fs" />
     </ItemGroup>

NightLight.Core.Tests/NightLightTests.fs

@@ -41,8 +41,7 @@ type NightLightTests() =
         |> Prop.label fakeHome.Label
         |> Prop.trivial (fakeHome.LightsThatAreOn.Length = 0)
 
-    // TODO: Bias generator for alarm cases so that `MaxTest` can be reduced
+    [<Property(Arbitrary = [| typeof<ArbitraryInteractions> |])>]
-    [<Property(Arbitrary = [| typeof<ArbitraryInteractions> |], MaxTest = 10_000)>]
     let ``All lights should either be off or have a brightness that fits its color`` (interactions: Interaction list) =
         let fakeHome = createFakeHomeWithNightLightAndInteract interactions
         let time = getTimeAfterInteractions interactions |> _.TimeOfDay