Clear ProcScheduler state each test run

Content.Tests/DMTests.cs

@@ -1,13 +1,12 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.Linq;
 using System.Threading.Tasks;
 using NUnit.Framework;
 using OpenDreamRuntime;
 using OpenDreamRuntime.Objects;
 using OpenDreamRuntime.Procs;
-using OpenDreamRuntime.Rendering;
-using OpenDreamShared.Rendering;
 using Robust.Shared.Asynchronous;
 using Robust.Shared.IoC;
 using Robust.Shared.Timing;
@@ -74,6 +73,8 @@ public void TestFiles(string sourceFile, DMTestFlags testFlags) {
                 return;
             }
 
+            _procScheduler.ClearState();
+
             Assert.That(compiledFile is not null && File.Exists(compiledFile), "Failed to compile DM source file");
             Assert.That(_dreamMan.LoadJson(compiledFile), $"Failed to load {compiledFile}");
             _dreamMan.StartWorld();
@@ -99,6 +100,9 @@ public void TestFiles(string sourceFile, DMTestFlags testFlags) {
                 Assert.That(returned?.IsTruthy(), Is.True, "Test was expected to return TRUE");
             }
 
+            var threads = _procScheduler.InspectThreads().ToList();
+            Assert.That(threads.Count == 0 && !_procScheduler.HasProcsSleeping && !_procScheduler.HasProcsQueued, $"One or more threads did not finish!");
+
             Cleanup(compiledFile);
             TestContext.WriteLine($"--- PASS {sourceFile}");
         } finally {

OpenDreamRuntime/Procs/ProcScheduler.cs

@@ -74,6 +74,17 @@ public void Process() {
         }
     }
 
+    /// <summary>
+    /// Clears all ProcScheduler state
+    /// </summary>
+    public void ClearState() {
+        _current = null;
+        _deferredTasks.Clear();
+        _sleeping.Clear();
+        _scheduled.Clear();
+        _tickers.Clear();
+    }
+
     public IEnumerable<DreamThread> InspectThreads() {
         // TODO: We shouldn't need to check if Thread is null here
         //       I think we're keeping disposed states somewhere here