Implement deterministic simulation spine

tests/SideScrollerGame.Sim.Tests/SimulationStepTests.cs

@@ -0,0 +1,103 @@
+using System.Collections.Immutable;
+using SideScrollerGame.Sim.Definitions;
+using SideScrollerGame.Sim.Input;
+
+namespace SideScrollerGame.Sim.Tests;
+
+public sealed class SimulationStepTests
+{
+    private sealed record UnsupportedAction : SimulationAction;
+
+    [Fact]
+    public void Step_AdvancesTickSnapshotsAndMovement()
+    {
+        Simulation simulation = new(SimulationTestFactory.CreateGameDefinition(), SimulationTestFactory.CreateConfig(), 7);
+
+        var result = simulation.Step(SimulationTestFactory.CreateTick(1, new MoveAxisChanged(new(1), 2, -1), new AimAxisChanged(new(1), 30, 40), new ButtonChanged(new(1), InputButton.Jump, true), new WeaponSlotSelected(new(1), 3)));
+
+        Assert.Equal(1, simulation.CurrentTick);
+        Assert.Equal(0, simulation.PreviousSnapshot.Tick);
+        Assert.Equal(0, result.PreviousSnapshot.Tick);
+        Assert.Equal(1, result.CurrentSnapshot.Tick);
+        Assert.Single(result.Events);
+
+        var player = simulation.CurrentState.GetRequiredPlayer(new(1));
+        Assert.Equal(12, player.Position.m_X.ToIntRound());
+        Assert.Equal(19, player.Position.m_Y.ToIntRound());
+        Assert.Equal(30, player.AimAxisX);
+        Assert.Equal(40, player.AimAxisY);
+        Assert.Equal(3, player.SelectedWeaponSlot);
+        Assert.NotEqual(0, player.ButtonMask);
+        Assert.Equal(result.StateHash, simulation.CurrentSnapshot.StateHash);
+        Assert.NotEqual(0UL, simulation.CurrentSnapshot.LastRandomValue);
+    }
+
+    [Fact]
+    public void Step_RejectsUnexpectedTickNumbers()
+    {
+        Simulation simulation = new(SimulationTestFactory.CreateGameDefinition(), SimulationTestFactory.CreateConfig(), 7);
+
+        var exception = Assert.Throws<InvalidOperationException>(() => simulation.Step(TickActionBatch.Empty(2)));
+
+        Assert.Contains("Expected tick 1", exception.Message);
+    }
+
+    [Fact]
+    public void Step_RejectsUnknownPlayers()
+    {
+        Simulation simulation = new(SimulationTestFactory.CreateGameDefinition(), SimulationTestFactory.CreateConfig(), 7);
+
+        var exception = Assert.Throws<InvalidOperationException>(() => simulation.Step(SimulationTestFactory.CreateTick(1, new MoveAxisChanged(new(99), 1, 0))));
+
+        Assert.Contains("Unknown player id 99", exception.Message);
+    }
+
+    [Fact]
+    public void Step_RejectsUnsupportedActions()
+    {
+        Simulation simulation = new(SimulationTestFactory.CreateGameDefinition(), SimulationTestFactory.CreateConfig(), 7);
+
+        var exception = Assert.Throws<NotSupportedException>(() => simulation.Step(SimulationTestFactory.CreateTick(1, new UnsupportedAction())));
+
+        Assert.Contains("Unsupported action type", exception.Message);
+    }
+
+    [Fact]
+    public void Constructor_RejectsDuplicatePlayers()
+    {
+        GameDefinition definition = new(ImmutableArray.Create(new(new(1), new(0, 0)), new PlayerDefinition(new(1), new(2, 3))));
+
+        var exception = Assert.Throws<InvalidOperationException>(() => new Simulation(definition, SimulationTestFactory.CreateConfig(), 11));
+
+        Assert.Contains("Duplicate player id 1", exception.Message);
+    }
+
+    [Fact]
+    public void Constructor_RejectsNullDefinition()
+    {
+        var exception = Assert.Throws<ArgumentNullException>(() => new Simulation(null!, SimulationTestFactory.CreateConfig(), 1));
+
+        Assert.Equal("gameDefinition", exception.ParamName);
+    }
+
+    [Fact]
+    public void Constructor_RejectsNullConfig()
+    {
+        var exception = Assert.Throws<ArgumentNullException>(() => new Simulation(SimulationTestFactory.CreateGameDefinition(), null!, 1));
+
+        Assert.Equal("config", exception.ParamName);
+    }
+
+    [Fact]
+    public void LoadState_RejectsNullDefinition()
+    {
+        var definition = SimulationTestFactory.CreateGameDefinition();
+        var config = SimulationTestFactory.CreateConfig();
+        Simulation simulation = new(definition, config, 2);
+        var bytes = simulation.SaveState();
+
+        var exception = Assert.Throws<ArgumentNullException>(() => Simulation.LoadState(bytes, null!, config));
+
+        Assert.Equal("gameDefinition", exception.ParamName);
+    }
+}