Implement native-backed SC0000 SFX lifecycle

engine/Age.Engine.Tests/SfxOpsTests.cs

@@ -0,0 +1,35 @@
+using System;
+using System.Collections.Generic;
+using Age.Engine.Model;
+using Age.Engine.Sys4;
+using Age.Engine.Vm;
+using Xunit;
+
+public class SfxOpsTests
+{
+    [Fact]
+    public void Sc0000SfxLifecycleAndBgmFadeReachHost()
+    {
+        var table = OpcodeTableJson.Load(Paths.OpcodesJson);
+        var script = ScriptAssembler.Assemble(table, "SFX",
+            new List<(int, Operand[])>
+            {
+                (0xb4, new[] { new Operand(0, 0x28), new Operand(0, 0) }),
+                (0xb5, new[] { new Operand(0, 0) }),
+                (0xb6, new[] { new Operand(0, 0) }),
+                (0xc2, new[] { new Operand(0, 25), new Operand(0, 3000) }),
+                (0xd9, Array.Empty<Operand>()),
+                (0x2, Array.Empty<Operand>()),
+            }, Array.Empty<string>());
+        var host = new RecordingHost();
+        var vm = new VirtualMachine(script, table, host);
+
+        vm.Run();
+
+        Assert.Equal("exit", vm.HaltReason);
+        Assert.Equal((0x28L, 0), Assert.Single(host.SfxLoads));
+        Assert.Equal(0, Assert.Single(host.SfxStarts));
+        Assert.Equal(0, Assert.Single(host.SfxReleases));
+        Assert.Equal((25, 3000L), Assert.Single(host.BgmFades));
+    }
+}