From ffc0fcaa43cd6368055ec73fae4f39fb03fd37fc Mon Sep 17 00:00:00 2001
From: gamer147 <gamer147@gmail.com>
Date: Sat, 6 Jun 2026 10:46:35 -0400
Subject: [PATCH] =?UTF-8?q?test(rng-seam):=20M12=20oracle=20=E2=80=94=20sc?=
 =?UTF-8?q?ripted=20RNG=20draws=20a=20known=20deck=20card=20(genuine=20mul?=
 =?UTF-8?q?ti-outcome=20roll)?=
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---
 .../RandomDrawOracleTests.cs                  | 67 +++++++++++++++++++
 1 file changed, 67 insertions(+)
 create mode 100644 SVSim.BattleEngine.Tests/RandomDrawOracleTests.cs

diff --git a/SVSim.BattleEngine.Tests/RandomDrawOracleTests.cs b/SVSim.BattleEngine.Tests/RandomDrawOracleTests.cs
new file mode 100644
index 0000000..d1bacd9
--- /dev/null
+++ b/SVSim.BattleEngine.Tests/RandomDrawOracleTests.cs
@@ -0,0 +1,67 @@
+using System.Linq;
+using NUnit.Framework;
+using SVSim.BattleEngine.Rng;
+using Wizard;
+using Wizard.Battle;
+
+namespace SVSim.BattleEngine.Tests
+{
+    // M12: the first card whose outcome is a GENUINE RNG roll. The M9 draw spell over a 3-card deck with
+    // IsRandomDraw=true selects via SkillRandomSelectFilter -> GetIns().StableRandom(poolCount), which
+    // HeadlessBattleMgr routes to the injected ScriptedRandomSource. The oracle asserts the engine drew
+    // EXACTLY the card the scripted roll selects, and (load-bearing) that the pick TRACKS the script:
+    // a different scripted unit draws a different card. This is the multi-outcome roll M9's one-card pool
+    // deliberately neutralized — it requires the F2 decoupling (real rolls under IsForecast) AND the
+    // IsRandomDraw=true second gate, both delivered by NewAuthoritativeBattle.
+    [TestFixture]
+    public class RandomDrawOracleTests
+    {
+        // Draw with a single scripted unit; return (drawnCardId, deckCountAfter). The deck is seeded with
+        // three distinguishable cards at indices 2,3,4 -> Index-order positions 0,1,2 map to
+        // RngDeckCardA/B/C. The draw makes one StableRandom(3) call -> index = floor(3*unit).
+        private static (int drawnId, int deckAfter) DrawWith(double unit)
+        {
+            var mgr = HeadlessEngineEnv.NewAuthoritativeBattle(new ScriptedRandomSource(new[] { unit }));
+            var player = mgr.BattlePlayer;
+
+            HeadlessEngineEnv.SeedDeck(mgr, HeadlessEngineEnv.RngDeckCardA, index: 2, isPlayer: true);
+            HeadlessEngineEnv.SeedDeck(mgr, HeadlessEngineEnv.RngDeckCardB, index: 3, isPlayer: true);
+            HeadlessEngineEnv.SeedDeck(mgr, HeadlessEngineEnv.RngDeckCardC, index: 4, isPlayer: true);
+
+            var spell = HeadlessEngineEnv.CreateHeadlessHandCard(HeadlessEngineEnv.RngDrawSpellId, 1, isPlayer: true, mgr);
+            player.HandCardList.Add(spell);
+            player.Pp = 10;
+
+            var pair = mgr.GetBattlePlayerPair(isPlayer: true);
+            var ap = new ActionProcessor(pair);
+            Assert.DoesNotThrow(() => ap.PlayCard(spell, selectedCards: null), "PlayCard threw on the random draw");
+
+            // The drawn card is the new hand entry that is not the spell.
+            var drawn = player.HandCardList.Single(c => c.CardId != HeadlessEngineEnv.RngDrawSpellId);
+            return (drawn.CardId, player.DeckCardList.Count);
+        }
+
+        [Test]
+        public void Random_draw_picks_the_scripted_card()
+        {
+            // unit 0.5 -> floor(3*0.5)=1 -> Index-order position 1 -> RngDeckCardB.
+            var (drawnId, deckAfter) = DrawWith(0.5);
+            Assert.Multiple(() =>
+            {
+                Assert.That(drawnId, Is.EqualTo(HeadlessEngineEnv.RngDeckCardB),
+                    "scripted roll 0.5 should draw the middle (Index-order position 1) deck card");
+                Assert.That(deckAfter, Is.EqualTo(2), "deck should be 3 -> 2 after drawing one");
+            });
+        }
+
+        [Test]
+        public void Random_draw_pick_tracks_the_scripted_roll()
+        {
+            // Load-bearing: varying the scripted unit must move the pick across all three positions.
+            // floor(3*0.0)=0 -> A ; floor(3*0.5)=1 -> B ; floor(3*0.9)=2 -> C.
+            Assert.That(DrawWith(0.0).drawnId, Is.EqualTo(HeadlessEngineEnv.RngDeckCardA), "0.0 -> position 0");
+            Assert.That(DrawWith(0.5).drawnId, Is.EqualTo(HeadlessEngineEnv.RngDeckCardB), "0.5 -> position 1");
+            Assert.That(DrawWith(0.9).drawnId, Is.EqualTo(HeadlessEngineEnv.RngDeckCardC), "0.9 -> position 2");
+        }
+    }
+}