Add test for IResettingEntitySystem resetting (#2442)

* Add test for IResettingEntitySystem resetting

* Fix test since a round start also resets systems

Content.IntegrationTests/Tests/ResettingEntitySystemTests.cs

@@ -0,0 +1,58 @@
+using System.Threading.Tasks;
+using Content.Server.GameTicking;
+using Content.Server.Interfaces.GameTicking;
+using Content.Shared.GameTicking;
+using NUnit.Framework;
+using Robust.Shared.GameObjects.Systems;
+using Robust.Shared.Interfaces.GameObjects;
+using Robust.Shared.IoC;
+
+namespace Content.IntegrationTests.Tests
+{
+    [TestFixture]
+    [TestOf(typeof(IResettingEntitySystem))]
+    public class ResettingEntitySystemTests : ContentIntegrationTest
+    {
+        private class TestResettingEntitySystem : EntitySystem, IResettingEntitySystem
+        {
+            public bool HasBeenReset { get; set; }
+
+            public void Reset()
+            {
+                HasBeenReset = true;
+            }
+        }
+
+        [Test]
+        public async Task ResettingEntitySystemResetTest()
+        {
+            var server = StartServer(new ServerContentIntegrationOption
+            {
+                ContentBeforeIoC = () =>
+                {
+                    IoCManager.Resolve<IEntitySystemManager>().LoadExtraSystemType<TestResettingEntitySystem>();
+                }
+            });
+
+            await server.WaitIdleAsync();
+
+            var gameTicker = server.ResolveDependency<IGameTicker>();
+            var entitySystemManager = server.ResolveDependency<IEntitySystemManager>();
+
+            await server.WaitAssertion(() =>
+            {
+                Assert.That(gameTicker.RunLevel, Is.EqualTo(GameRunLevel.InRound));
+
+                var system = entitySystemManager.GetEntitySystem<TestResettingEntitySystem>();
+
+                system.HasBeenReset = false;
+
+                Assert.False(system.HasBeenReset);
+
+                gameTicker.RestartRound();
+
+                Assert.True(system.HasBeenReset);
+            });
+        }
+    }
+}