Project-M/Assets/_Project/Tests/EditMode/HeartbeatSystemTests.cs

using NUnit.Framework;
using Unity.Entities;
using ProjectM.Simulation;

namespace ProjectM.Tests
{
    /// <summary>
    /// Setup smoke test: proves the DOTS toolchain compiles, source-generates, and ticks.
    /// Boots a bare ECS world, registers <see cref="HeartbeatSystem"/> in the
    /// SimulationSystemGroup, and asserts the component advances once per group update.
    /// (Netcode client/server world boot is covered separately by the §3 Play Mode check.)
    /// </summary>
    public class HeartbeatSystemTests
    {
        [Test]
        public void Heartbeat_Advances_Once_Per_SimulationGroup_Tick()
        {
            using var world = new World("HeartbeatTestWorld");
            var simulationGroup = world.GetOrCreateSystemManaged<SimulationSystemGroup>();
            var heartbeatSystem = world.GetOrCreateSystem<HeartbeatSystem>();
            simulationGroup.AddSystemToUpdateList(heartbeatSystem);
            simulationGroup.SortSystems();

            var entityManager = world.EntityManager;
            var entity = entityManager.CreateEntity(typeof(Heartbeat));

            Assert.AreEqual(0, entityManager.GetComponentData<Heartbeat>(entity).Tick,
                "Heartbeat should start at 0.");

            const int ticks = 8;
            for (int i = 0; i < ticks; i++)
            {
                simulationGroup.Update();
            }

            Assert.AreEqual(ticks, entityManager.GetComponentData<Heartbeat>(entity).Tick,
                "Heartbeat.Tick should advance exactly once per SimulationSystemGroup update.");
        }
    }
}