diff --git a/STPTests/TestWIGConcurrencyChanges.cs b/STPTests/TestWIGConcurrencyChanges.cs
index 64dbc8f..93723cc 100644
--- a/STPTests/TestWIGConcurrencyChanges.cs
+++ b/STPTests/TestWIGConcurrencyChanges.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Diagnostics;
 using System.Threading;
 using NUnit.Framework;
 
@@ -13,9 +14,6 @@ namespace WorkItemsGroupTests
 	[Category("TestWIGConcurrencyChanges")]
 	public class TestWIGConcurrencyChanges
 	{
-	    /// <summary>
-        /// Example of waiting for idle
-        /// </summary>
         [Test]
         public void TestWIGConcurrencyChange1WIG()
         {
@@ -57,9 +55,6 @@ namespace WorkItemsGroupTests
             smartThreadPool.Shutdown();
         }
 
-        /// <summary>
-        /// Example of waiting for idle
-        /// </summary>
         [Test]
         public void TestWIGConcurrencyChange2WIGs()
         {
@@ -141,67 +136,57 @@ namespace WorkItemsGroupTests
             return 1;
         }
 
-
-
-
-/*
-        /// <summary>
-        /// Example of waiting for idle
-        /// </summary>
         [Test]
-        public void WaitForIdle() 
-        { 
-            SmartThreadPool smartThreadPool = new SmartThreadPool(10*1000, 25, 0);
+        public void TestWIGConcurrencyChange()
+        {
+            SmartThreadPool smartThreadPool = new SmartThreadPool(10 * 1000, 25, 0);
 
+            IWorkItemsGroup wig = smartThreadPool.CreateWorkItemsGroup(smartThreadPool.MaxThreads);
             bool success = false;
 
-            for(int i = 0; i < 100; ++i)
+            for (int i = 0; i < 100; ++i)
             {
-                smartThreadPool.QueueWorkItem(
-                    new WorkItemCallback(this.DoSomeWork), 
-                    null);
+                wig.QueueWorkItem(new WorkItemCallback(this.DoSomeLongWork), null);
             }
 
-            success = !smartThreadPool.WaitForIdle(3500);
-            success = success && smartThreadPool.WaitForIdle(1000);
+            wig.Concurrency = 1;
+            success = WaitForWIGThreadsInUse(wig, 1, 1 * 1000);
+            Assert.IsTrue(success);
+
+            wig.Concurrency = 5;
+            success = WaitForWIGThreadsInUse(wig, 5, 2 * 1000);
+            Assert.IsTrue(success);
+
+            wig.Concurrency = 25;
+            success = WaitForWIGThreadsInUse(wig, 25, 4 * 1000);
+            Assert.IsTrue(success);
+
+            wig.Concurrency = 10;
+            success = WaitForWIGThreadsInUse(wig, 10, 10 * 1000);
+            Assert.IsTrue(success);
 
             smartThreadPool.Shutdown();
-
-            Assert.IsTrue(success);
-        } 
-
-		[Test]
-		public void WaitForIdleOnWrongThread() 
-		{ 
-			SmartThreadPool smartThreadPool = new SmartThreadPool(10*1000, 25, 0);
-
-			IWorkItemResult wir = smartThreadPool.QueueWorkItem(
-				new WorkItemCallback(this.DoWaitForIdle), 
-				smartThreadPool);
-
-			Exception e;
-			wir.GetResult(out e);
-
-			smartThreadPool.Shutdown();
-
-			Assert.IsTrue(e is NotSupportedException);
-		} 
-
-
-        private int x = 0;
-        private object DoSomeWork(object state)
-        { 
-            Debug.WriteLine(Interlocked.Increment(ref x));
-            Thread.Sleep(1000);
-            return 1;
         }
 
-		private object DoWaitForIdle(object state)
-		{ 
-			SmartThreadPool smartThreadPool = state as SmartThreadPool;
-			smartThreadPool.WaitForIdle();
-			return null;
-		}
- */ 
-	}
+
+        private bool WaitForWIGThreadsInUse(IWorkItemsGroup wig, int maxThreadsCount, int timeout)
+        {
+            DateTime end = DateTime.Now + new TimeSpan(0, 0, 0, 0, timeout);
+
+            bool success = false;
+            while (DateTime.Now <= end && !success)
+            {
+                success = (wig.InUseThreads == maxThreadsCount);
+                Thread.Sleep(10);
+            }
+
+            return success;
+        }
+
+        private object DoSomeLongWork(object state)
+        {
+            Thread.Sleep(250);
+            return 1;
+        }
+    }
 }
diff --git a/SmartThreadPool/Interfaces.cs b/SmartThreadPool/Interfaces.cs
index a25a499..f23205d 100644
--- a/SmartThreadPool/Interfaces.cs
+++ b/SmartThreadPool/Interfaces.cs
@@ -84,6 +84,11 @@ namespace Amib.Threading
         /// </summary>
         int WaitingCallbacks { get; }
 
+        /// <summary>
+        /// Get the number of currently executing work items
+        /// </summary>
+        int InUseThreads { get; }
+
         /// <summary>
         /// Get an array with all the state objects of the currently running items.
         /// The array represents a snap shot and impact performance.
diff --git a/SmartThreadPool/SmartThreadPool.cs b/SmartThreadPool/SmartThreadPool.cs
index a4f4ce5..fc25c21 100644
--- a/SmartThreadPool/SmartThreadPool.cs
+++ b/SmartThreadPool/SmartThreadPool.cs
@@ -1395,18 +1395,6 @@ namespace Amib.Threading
 			} 
 		}
 
-		/// <summary>
-		/// Get the number of busy (not idle) threads in the thread pool.
-		/// </summary>
-		public int InUseThreads 
-		{ 
-			get 
-			{ 
-				ValidateNotDisposed();
-				return _inUseWorkerThreads; 
-			} 
-		}
-
         /// <summary>
         /// Returns true if the current running work item has been cancelled.
         /// Must be used within the work item's callback method.
@@ -1508,6 +1496,18 @@ namespace Amib.Threading
 	        set { MaxThreads = value; }
 	    }
 
+        /// <summary>
+        /// Get the number of busy (not idle) threads in the thread pool.
+        /// </summary>
+        public override int InUseThreads
+        {
+            get
+            {
+                ValidateNotDisposed();
+                return _inUseWorkerThreads;
+            }
+        }
+
 	    /// <summary>
 	    /// Get the number of work items in the queue.
 	    /// </summary>
diff --git a/SmartThreadPool/WorkItemsGroup.cs b/SmartThreadPool/WorkItemsGroup.cs
index d9d34ac..a78c78c 100644
--- a/SmartThreadPool/WorkItemsGroup.cs
+++ b/SmartThreadPool/WorkItemsGroup.cs
@@ -126,6 +126,14 @@ namespace Amib.Threading.Internal
             }
         }
 
+        public override int InUseThreads
+        {
+            get
+            {
+                return _workItemsExecutingInStp;
+            }
+        }
+
         public override int WaitingCallbacks
         {
             get { return _workItemsQueue.Count; }
diff --git a/SmartThreadPool/WorkItemsGroupBase.cs b/SmartThreadPool/WorkItemsGroupBase.cs
index b629c51..c6c0fdb 100644
--- a/SmartThreadPool/WorkItemsGroupBase.cs
+++ b/SmartThreadPool/WorkItemsGroupBase.cs
@@ -39,6 +39,8 @@ namespace Amib.Threading.Internal
 
         public abstract int Concurrency { get; set; }
         public abstract int WaitingCallbacks { get; }
+        public abstract int InUseThreads { get; }
+
         public abstract object[] GetStates();
         public abstract WIGStartInfo WIGStartInfo { get; }
         public abstract void Start();