gistfile1.txt

    public struct MyComponent : IComponentData
    {
        public Entity Reference;
        public int Value;
    }

    public struct MyElement : IBufferElementData
    {
        public Entity Reference;
        public int Value;
    }

    public class MySystem : SystemBase
    {
        protected override void OnUpdate()
        {
            var ecb = new EntityCommandBuffer(Allocator.Temp);
            var entity = ecb.CreateEntity();
            ecb.AddComponent(entity, new MyComponent
            {
                Reference = entity,
                Value = 42,
            });
            var buffer = ecb.AddBuffer<MyElement>(entity);
            buffer.Add(new MyElement
            {
                Reference = entity,
                Value = 41
            });
            ecb.Playback(EntityManager);

            var createdEntity = GetSingletonEntity<MyComponent>();
            var createdComponent = GetSingleton<MyComponent>();

            Assert.AreEqual(createdComponent.Reference, createdEntity);
            Assert.AreNotEqual(createdEntity, entity);
            Assert.AreEqual(createdComponent.Value, 42);

            var createdBuffer = EntityManager.GetBuffer<MyElement>(createdEntity);
            
            Assert.AreEqual(createdBuffer[0].Reference, createdEntity);
            Assert.AreEqual(createdBuffer[0].Value, 41);
        }
    }

    [Test]
    unsafe public void ECBReferenceTest()
    {
        World.GetOrCreateSystem<MySystem>().Update();
    }