more granular Concurrency control.

indexer calls are done fully paralleled.
events are dispatched on max of 2 threads.

NzbDrone.Test.Common/ConcurrencyCounter.cs

@@ -0,0 +1,57 @@
+using System;
+using System.Collections.Generic;
+using System.Threading;
+
+namespace NzbDrone.Test.Common
+{
+    public class ConcurrencyCounter
+    {
+        private int _items;
+        readonly object _mutex = new object();
+        readonly Dictionary<int, int> _threads = new Dictionary<int, int>();
+
+        public int MaxThreads { get { return _threads.Count; } }
+
+        public ConcurrencyCounter(int items)
+        {
+            _items = items;
+        }
+
+        public void WaitForAllItems()
+        {
+            while (_items != 0)
+            {
+                Thread.Sleep(500);
+            }
+        }
+
+        public int Start()
+        {
+            int threadId = Thread.CurrentThread.ManagedThreadId;
+            lock (_mutex)
+            {
+
+                _threads[threadId] = 1;
+            }
+
+            Console.WriteLine("Starting " + threadId);
+            return threadId;
+        }
+
+        public void SimulateWork(int sleepInMs)
+        {
+            var id = Start();
+            Thread.Sleep(sleepInMs);
+            Stop(id);
+        }
+
+        public void Stop(int id)
+        {
+            Console.WriteLine("Finished " + id);
+            lock (_mutex)
+            {
+                _items--;
+            }
+        }
+    }
+}

NzbDrone.Test.Common/NzbDrone.Test.Common.csproj

@@ -90,6 +90,7 @@
     <Compile Include="AutoMoq\AutoMoqer.cs" />
     <Compile Include="AutoMoq\Unity\AutoMockingBuilderStrategy.cs" />
     <Compile Include="AutoMoq\Unity\AutoMockingContainerExtension.cs" />
+    <Compile Include="ConcurrencyCounter.cs" />
     <Compile Include="ExceptionVerification.cs" />
     <Compile Include="Categories\IntegrationTestAttribute.cs" />
     <Compile Include="LoggingTest.cs" />