feat: add block model with IBlock flyweight and registry

VoxelEngine.Tests/BlockRegistryTests.cs

@@ -0,0 +1,52 @@
+using VoxelEngine.World;
+using VoxelEngine.World.Blocks;
+using Xunit;
+
+namespace VoxelEngine.Tests;
+
+public class BlockRegistryTests
+{
+    [Fact]
+    public void Get_ReturnsRegisteredBlockById()
+    {
+        var registry = new BlockRegistry();
+
+        Assert.IsType<AirBlock>(registry.Get(0));
+        Assert.IsType<StoneBlock>(registry.Get(1));
+        Assert.IsType<DirtBlock>(registry.Get(2));
+        Assert.IsType<GrassBlock>(registry.Get(3));
+    }
+
+    [Fact]
+    public void Air_IsNotOpaqueOrSolid_OthersAre()
+    {
+        var registry = new BlockRegistry();
+
+        Assert.False(registry.Get(0).IsOpaque);
+        Assert.False(registry.Get(0).IsSolid);
+        Assert.True(registry.Get(1).IsOpaque);
+        Assert.True(registry.Get(1).IsSolid);
+    }
+
+    [Fact]
+    public void Grass_HasDifferentTexturesPerFace()
+    {
+        var registry = new BlockRegistry();
+        IBlock grass = registry.Get(3);
+
+        Assert.Equal(0, grass.GetTextureIndex(BlockFace.Top));
+        Assert.Equal(1, grass.GetTextureIndex(BlockFace.Bottom));
+        Assert.Equal(3, grass.GetTextureIndex(BlockFace.North));
+    }
+
+    [Fact]
+    public void NamedAccessors_MatchIds()
+    {
+        var registry = new BlockRegistry();
+
+        Assert.Equal((ushort)0, registry.Air.Id);
+        Assert.Equal((ushort)1, registry.Stone.Id);
+        Assert.Equal((ushort)2, registry.Dirt.Id);
+        Assert.Equal((ushort)3, registry.Grass.Id);
+    }
+}