Remote execution from the UI

The UI now executes the tests in a separate process.  This removes the
need to shadow copy and frees up the idea of re-running the tests
without restart of the UI.

xunit.runner.wpf/Impl/RemoteTestUtil .RunSession.cs

@@ -0,0 +1,74 @@
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+using System.IO.Pipes;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using System.Windows.Threading;
+using xunit.runner.data;
+using xunit.runner.wpf.ViewModel;
+
+namespace xunit.runner.wpf.Impl
+{
+    internal partial class RemoteTestUtil 
+    {
+        private sealed class RunSession : ITestRunSession
+        {
+            private const int MaxResultPerTick = 100;
+
+            private readonly Connection _connection;
+            private readonly ConcurrentQueue<TestResultData> _resultQueue;
+            private readonly DispatcherTimer _timer;
+            private bool _closed;
+            private event EventHandler<TestResultEventArgs> _testFinished;
+
+            internal RunSession(Connection connection, Dispatcher dispatcher, ConcurrentQueue<TestResultData> resultQueue)
+            {
+                _connection = connection;
+                _resultQueue = resultQueue;
+                _timer = new DispatcherTimer(TimeSpan.FromMilliseconds(100), DispatcherPriority.Normal, OnTimerTick, dispatcher);
+            }
+
+            private void OnTimerTick(object sender, EventArgs e)
+            {
+                var i = 0;
+                TestResultData data;
+                while (i < MaxResultPerTick && _resultQueue.TryDequeue(out data))
+                {
+                    if (data == null)
+                    {
+                        Close();
+                        break;
+                    }
+
+                    _testFinished?.Invoke(this, new TestResultEventArgs(data.TestCaseDisplayName, data.TestState));
+                }
+            }
+
+            internal void Close()
+            {
+                if (_closed)
+                {
+                    return;
+                }
+
+                _closed = true;
+                _timer.Stop();
+                ((IDisposable)_connection).Dispose();
+            }
+
+            #region ITestRunSession
+
+            event EventHandler<TestResultEventArgs> ITestRunSession.TestFinished
+            {
+                add { _testFinished += value; }
+                remove { _testFinished -= value; }
+            }
+
+            #endregion
+        }
+    }
+}