CommandBuffer Tests And Fixes (#160)

* - Added some more tests covering the `CommandBuffer`. Fixed a bug in `Create` method, sometimes assigning duplicate IDs.
 - Removed all conditional access in `Playback` and `Dispose`, those things are never null.
 - Added ArrayExtensions tests.

* Simplified ID generation

src/Arch.Tests/CommandBufferTest.cs

@@ -73,6 +73,116 @@ public void CommandBuffer()
         World.Destroy(world);
     }
 
+    [Test]
+    public void CommandBufferCreateMultipleEntities()
+    {
+        var world = World.Create();
+
+        var entities = new List<Entity>();
+        using (var commandBuffer = new CommandBuffer.CommandBuffer(world))
+        {
+            entities.Add(commandBuffer.Create(new ComponentType[] { typeof(Transform) }));
+            entities.Add(commandBuffer.Create(new ComponentType[] { typeof(Transform) }));
+            entities.Add(commandBuffer.Create(new ComponentType[] { typeof(Transform) }));
+            commandBuffer.Playback();
+        }
+
+        That(world.Size, Is.EqualTo(entities.Count));
+
+        World.Destroy(world);
+    }
+
+    [Test]
+    public void CommandBufferCreateAndDestroy()
+    {
+        var world = World.Create();
+
+        using (var commandBuffer = new CommandBuffer.CommandBuffer(world))
+        {
+            commandBuffer.Create(new ComponentType[] { typeof(Transform) });
+            commandBuffer.Create(new ComponentType[] { typeof(Transform) });
+            var e = commandBuffer.Create(new ComponentType[] { typeof(Transform) });
+            commandBuffer.Destroy(e);
+            commandBuffer.Playback();
+        }
+
+        That(world.Size, Is.EqualTo(2));
+
+        var query = new QueryDescription { All = new ComponentType[] { typeof(Transform) } };
+        var entities = new Entity[world.CountEntities(query)];
+        world.GetEntities(query, entities);
+
+        using (var commandBuffer = new CommandBuffer.CommandBuffer(world))
+        {
+            commandBuffer.Destroy(entities[0]);
+            commandBuffer.Playback();
+        }
+
+        That(world.Size, Is.EqualTo(1));
+
+        World.Destroy(world);
+    }
+
+    [Test]
+    public void CommandBufferModify()
+    {
+        var world = World.Create();
+
+        // Create an entity
+        using (var commandBuffer = new CommandBuffer.CommandBuffer(world))
+        {
+            commandBuffer.Create(new ComponentType[] { typeof(int) });
+            commandBuffer.Playback();
+        }
+
+        That(world.Size, Is.EqualTo(1));
+
+        // Retrieve the entity we just created
+        var query = new QueryDescription { All = new ComponentType[] { typeof(int) } };
+        var entities = new Entity[world.CountEntities(query)];
+        world.GetEntities(query, entities);
+
+        // Check that it doesn't yet have anything
+        Multiple(() =>
+        {
+            That(world.TryGet<Transform>(entities[0], out _), Is.False);
+            That(world.TryGet<Rotation>(entities[0], out _), Is.False);
+        });
+
+        // Add to it
+        using (var commandBuffer = new CommandBuffer.CommandBuffer(world))
+        {
+            commandBuffer.Add<Transform>(entities[0]);
+            commandBuffer.Add<Rotation>(entities[0]);
+            commandBuffer.Playback();
+        }
+
+        // Check modification added things
+        Multiple(() =>
+        {
+            That(world.TryGet<Transform>(entities[0], out _), Is.True);
+            That(world.TryGet<Rotation>(entities[0], out _), Is.True);
+        });
+
+        // Remove from it
+        using (var commandBuffer = new CommandBuffer.CommandBuffer(world))
+        {
+            commandBuffer.Remove<Rotation>(entities[0]);
+            commandBuffer.Playback();
+        }
+
+        // Check modification removed rotation
+        Multiple(() =>
+        {
+            That(world.TryGet<Transform>(entities[0], out _), Is.True);
+            That(world.TryGet<Rotation>(entities[0], out _), Is.False);
+        });
+
+
+
+        World.Destroy(world);
+    }
+
     [Test]
     public void CommandBufferCombined()
     {

src/Arch.Tests/Extensions/ArrayExtensionsTests.cs

@@ -0,0 +1,59 @@
+using Arch.Core.Extensions.Internal;
+
+namespace Arch.Tests.Extensions;
+
+[TestFixture]
+public class ArrayExtensionsTests
+{
+    [Test]
+    public void Add_InRange()
+    {
+        var arr = new[] { 1, 2, 3 };
+        arr.Add(0, 7);
+
+        CollectionAssert.AreEqual(new[] { 7, 2, 3 }, arr);
+    }
+
+    [Test]
+    public void Add_OutOfRange()
+    {
+        var arr = new[] { 1, 2, 3 };
+        arr = arr.Add(3, 7);
+
+        // The array might be any size now.
+        // All we need to check if that the first 4 elements are correct.
+        CollectionAssert.AreEqual(new[] { 1, 2, 3, 7 }, arr.Take(4));
+    }
+
+    [Test]
+    public void Add_FarOutOfRange()
+    {
+        var arr = new[] { 1, 2, 3 };
+        arr = arr.Add(30, 7);
+
+        // The array might be any size now.
+        // All we need to check if that the first 3 elements are correct and the 30th is 7.
+        CollectionAssert.AreEqual(new[] { 1, 2, 3 }, arr.Take(3));
+        Assert.That(arr[30], Is.EqualTo(7));
+    }
+
+    [Test]
+    public void Add_VeryFarOutOfRange()
+    {
+        var arr = new[] { 1, 2, 3 };
+        arr = arr.Add(3000, 7);
+
+        // The array might be any size now.
+        // All we need to check if that the first 3 elements are correct and the 30th is 7.
+        CollectionAssert.AreEqual(new[] { 1, 2, 3 }, arr.Take(3));
+        Assert.That(arr[3000], Is.EqualTo(7));
+    }
+
+    [Test]
+    public void Add_NegativeIndex()
+    {
+        var arr = new[] { 1, 2, 3 };
+
+        Assert.Throws<ArgumentOutOfRangeException>(() => arr.Add(-1, 7));
+    }
+}

src/Arch/CommandBuffer/CommandBuffer.cs

@@ -177,7 +177,7 @@ public Entity Create(ComponentType[] types)
     {
         lock (this)
         {
-            var entity = new Entity(-Math.Abs(Size - 1), World.Id);
+            var entity = new Entity(-(Size + 1), World.Id);
             Register(entity, out _);
 
             var command = new CreateCommand(Size - 1, types);
@@ -433,31 +433,31 @@ public void Playback()
 
         // Reset values.
         Size = 0;
-        Entities?.Clear();
-        BufferedEntityInfo?.Clear();
-        Creates?.Clear();
-        Sets?.Clear();
-        Adds?.Clear();
-        Removes?.Clear();
-        Destroys?.Clear();
-        _addTypes?.Clear();
-        _removeTypes?.Clear();
+        Entities.Clear();
+        BufferedEntityInfo.Clear();
+        Creates.Clear();
+        Sets.Clear();
+        Adds.Clear();
+        Removes.Clear();
+        Destroys.Clear();
+        _addTypes.Clear();
+        _removeTypes.Clear();
     }
 
     /// <summary>
     ///     Disposes the <see cref="CommandBuffer"/>.
     /// </summary>
     public void Dispose()
     {
-        Entities?.Dispose();
-        BufferedEntityInfo?.Dispose();
-        Creates?.Clear();
-        Sets?.Clear();
-        Adds?.Clear();
-        Removes?.Clear();
-        Destroys?.Dispose();
-        _addTypes?.Dispose();
-        _removeTypes?.Dispose();
+        Entities.Dispose();
+        BufferedEntityInfo.Dispose();
+        Creates.Clear();
+        Sets.Clear();
+        Adds.Clear();
+        Removes.Clear();
+        Destroys.Dispose();
+        _addTypes.Dispose();
+        _removeTypes.Dispose();
         GC.SuppressFinalize(this);
     }
 }