feat: add Chunk as a dense 16-cubed id array

VoxelEngine.Tests/ChunkTests.cs

@@ -0,0 +1,40 @@
+using VoxelEngine.World;
+using Xunit;
+
+namespace VoxelEngine.Tests;
+
+public class ChunkTests
+{
+    [Fact]
+    public void Size_Is16()
+    {
+        Assert.Equal(16, Chunk.Size);
+    }
+
+    [Fact]
+    public void NewChunk_IsAllAir()
+    {
+        var chunk = new Chunk();
+        Assert.Equal((ushort)0, chunk[0, 0, 0]);
+        Assert.Equal((ushort)0, chunk[15, 15, 15]);
+    }
+
+    [Fact]
+    public void Indexer_StoresAndReturnsId()
+    {
+        var chunk = new Chunk();
+        chunk[1, 2, 3] = 7;
+        Assert.Equal((ushort)7, chunk[1, 2, 3]);
+        Assert.Equal((ushort)0, chunk[3, 2, 1]);
+    }
+
+    [Theory]
+    [InlineData(0, 0, 0, true)]
+    [InlineData(15, 15, 15, true)]
+    [InlineData(-1, 0, 0, false)]
+    [InlineData(0, 16, 0, false)]
+    public void InBounds_ChecksCoordinates(int x, int y, int z, bool expected)
+    {
+        Assert.Equal(expected, Chunk.InBounds(x, y, z));
+    }
+}