1 files changed, 35 insertions, 0 deletions
diff --git a/src/LivingVillage.Desktop.Tests/PrototypeTests.fs b/src/LivingVillage.Desktop.Tests/PrototypeTests.fs
index 7e4ce5f..d77abd6 100644
--- a/src/LivingVillage.Desktop.Tests/PrototypeTests.fs
+++ b/src/LivingVillage.Desktop.Tests/PrototypeTests.fs
@@ -670,6 +670,41 @@ type PrototypeTests () =
         Assert.AreEqual<string option>(None, M5Interaction.refreshPrompt world needsView |> fun value -> value.Prompt)
 
     [<TestMethod>]
+    member _.DayPhaseLightingIsPureDeterministicAndTransitionsSmoothly () =
+        let ticksPerHour = Sim.ticksPerDay / 24L
+        let atHour hour = M6Presentation.lightingAtTick (int64 hour * ticksPerHour)
+
+        // Anchors: full day at noon, full night at midnight, no drift.
+        Assert.AreEqual<float32>(0.0f, (atHour 12).Blend)
+        Assert.AreEqual<float32>(1.0f, (atHour 0).Blend)
+        Assert.AreEqual<float32>(1.0f, (atHour 2).Blend)
+
+        // Dawn ramp: 4:00 -> 6:00 goes night -> day, monotonic.
+        let dawnStart = (atHour 4).Blend
+        let dawnMid = (M6Presentation.lightingAtTick (int64 5 * ticksPerHour)).Blend
+        let dawnEnd = (atHour 6).Blend
+        Assert.AreEqual<float32>(1.0f, dawnStart)
+        Assert.AreEqual<float32>(0.5f, dawnMid)
+        Assert.AreEqual<float32>(0.0f, dawnEnd)
+
+        // Dusk ramp 20:00 -> 22:00 goes day -> night monotonically.
+        let duskStart = (atHour 20).Blend
+        let duskMid = (M6Presentation.lightingAtTick (int64 21 * ticksPerHour)).Blend
+        let duskEnd = (atHour 22).Blend
+        Assert.AreEqual<float32>(0.0f, duskStart)
+        Assert.AreEqual<float32>(0.5f, duskMid)
+        Assert.AreEqual<float32>(1.0f, duskEnd)
+
+        // Determinism without randomness.
+        let once = atHour 13
+        let twice = atHour 13
+        Assert.AreEqual<M6RenderProfile>(once, twice)
+
+        // Lantern glow: warm halo only rises with night blend.
+        Assert.AreEqual<float32>(0.0f, (atHour 13).LanternGlow)
+        Assert.AreEqual<float32>(1.0f, (atHour 0).LanternGlow)
+
+    [<TestMethod>]
     member _.WorldPanelDoesNotRenderA永久KeyList () =
         let world = Sim.initialWorldN 42UL 0
         let lines = M5Interaction.panelLines world M5Interaction.initial