Implement deterministic simulation spine

tests/SideScrollerGame.Sim.Tests/SimulationStateTests.cs

@@ -0,0 +1,46 @@
+using System.Collections.Immutable;
+using SideScrollerGame.Sim.Input;
+using SideScrollerGame.Sim.Runtime;
+
+namespace SideScrollerGame.Sim.Tests;
+
+public sealed class SimulationStateTests
+{
+    [Fact]
+    public void PlayerState_CloneAndButtonReleasePreserveIndependentState()
+    {
+        PlayerState player = new(new(1), new(3, 4), 1, 2, 5, 6, 7, 0);
+        player.SetButton(InputButton.Dash, true);
+
+        var clone = player.Clone();
+        player.SetButton(InputButton.Dash, false);
+
+        Assert.NotEqual(player.ButtonMask, clone.ButtonMask);
+        Assert.Equal(7, clone.SelectedWeaponSlot);
+        Assert.Equal(3, clone.Position.m_X.ToIntRound());
+        Assert.Equal(4, clone.Position.m_Y.ToIntRound());
+    }
+
+    [Fact]
+    public void SimulationState_CloneCreatesDeepCopy()
+    {
+        SimulationState original = new(4, 9, 123UL, 456UL, ImmutableArray.Create(new PlayerState(new(1), new(1, 2), 3, 4, 5, 6, 7, 8)));
+        var clone = original.Clone();
+
+        original.GetRequiredPlayer(new(1)).SetMoveAxis(9, 9);
+
+        Assert.Equal(4, clone.Tick);
+        Assert.Equal(9, clone.Seed);
+        Assert.Equal((ulong)123, clone.RandomState);
+        Assert.Equal((ulong)456, clone.LastRandomValue);
+        Assert.Equal(3, clone.GetRequiredPlayer(new(1)).MoveAxisX);
+    }
+
+    [Fact]
+    public void SimulationState_AcceptsDefaultPlayerArray()
+    {
+        SimulationState state = new(0, 1, 1UL, 0UL, default);
+
+        Assert.Empty(state.Players);
+    }
+}