Stat checks: check command with stat roll outcomes and its schema

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/DiceRollTests.cs

@@ -0,0 +1,38 @@
+namespace Cthangover.Mods.StatChecks.Tests
+{
+    using System;
+    using Cthangover.Core.Mods.Testing;
+
+    /// <summary>Tabletop dice notation: valid forms roll within their range, "no dice" rolls 0, typos roll 0 and are invalid.</summary>
+    public class DiceRollTests
+    {
+        [ModTest("dice/notation")]
+        static void Notation(ModTestContext ctx)
+        {
+            ModAssert.True(DiceRoll.TryParse("2d6", out var count, out var sides) && count == 2 && sides == 6, "2d6");
+            ModAssert.True(DiceRoll.TryParse("D20", out count, out sides) && count == 1 && sides == 20, "d20 in any case");
+            ModAssert.True(DiceRoll.TryParse("none", out count, out _) && count == 0, "none");
+            ModAssert.True(DiceRoll.TryParse("", out count, out _) && count == 0, "empty");
+            foreach (var bad in new[] { "d1", "2x6", "-1d6", "d", "3d", "1000d6", "1.5d6" })
+                ModAssert.False(DiceRoll.IsValid(bad), $"'{bad}' is not dice");
+        }
+
+        [ModTest("dice/rolls_stay_in_range")]
+        static void RollsStayInRange(ModTestContext ctx)
+        {
+            var random = new Random(3);
+            var seenLow = false;
+            var seenHigh = false;
+            for (var i = 0; i < 400; i++)
+            {
+                var roll = DiceRoll.Roll("2d6", random);
+                ModAssert.True(roll >= 2 && roll <= 12, $"2d6 gave {roll}");
+                seenLow |= roll == 2;
+                seenHigh |= roll == 12;
+            }
+            ModAssert.True(seenLow && seenHigh, "both ends of 2d6 come up in 400 rolls");
+            ModAssert.Equal(0, DiceRoll.Roll("none"), "no dice");
+            ModAssert.Equal(0, DiceRoll.Roll("oops"), "a typo rolls nothing");
+        }
+    }
+}