Fix issue with checking if session file available

Change to check length of sessionPath file and only if file exists test passes.
Update to use CodeBase which is the original location of the file under bin dir.  Location is in the temp dir when run under xUnit.

Author: rkeithhill

test/PowerShellEditorServices.Test.Host/ServerTestsBase.cs

@@ -10,9 +10,7 @@
 using System.Collections.Concurrent;
 using System.Diagnostics;
 using System.IO;
-#if CoreCLR
 using System.Reflection;
-#endif
 using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
@@ -21,6 +19,7 @@ namespace Microsoft.PowerShell.EditorServices.Test.Host
 {
     public class ServerTestsBase
     {
+        private static int sessionCounter;        
         private Process serviceProcess;
         protected IMessageSender messageSender;
         protected IMessageHandlers messageHandlers;
@@ -39,15 +38,18 @@ protected async Task<Tuple<int, int>> LaunchService(
             string scriptPath = Path.Combine(modulePath, "Start-EditorServices.ps1");
 
 #if CoreCLR
-            string assemblyPath = this.GetType().GetTypeInfo().Assembly.Location;
-            FileVersionInfo fileVersionInfo =
-                FileVersionInfo.GetVersionInfo(assemblyPath);
+            Assembly assembly = this.GetType().GetTypeInfo().Assembly;
 #else
-            string assemblyPath = this.GetType().Assembly.Location;
+            Assembly assembly = this.GetType().Assembly;
+#endif
+
+            string assemblyPath = new Uri(assembly.CodeBase).LocalPath;
             FileVersionInfo fileVersionInfo =
                 FileVersionInfo.GetVersionInfo(assemblyPath);
-#endif
-            string sessionPath = Path.Combine(Path.GetDirectoryName(assemblyPath), "session.json");
+
+            string sessionPath = 
+                Path.Combine(
+                    Path.GetDirectoryName(assemblyPath), $"session-{++sessionCounter}.json");
 
             string editorServicesModuleVersion =
                 string.Format(
@@ -105,7 +107,7 @@ protected async Task<Tuple<int, int>> LaunchService(
             this.serviceProcess.Start();
 
             // Wait for the server to finish initializing
-            while(!File.Exists(sessionPath) && new FileInfo(assemblyPath).Length > 0)
+            while (!File.Exists(sessionPath) || (new FileInfo(sessionPath).Length == 0))
             {
                 Thread.Sleep(100);
             }