Make diagnostics client library tests not sleep

src/tests/Microsoft.Diagnostics.NETCore.Client/EventPipeSessionTests.cs

@@ -55,7 +55,7 @@ public void BasicEventPipeSessionTest()
         public void EventPipeSessionStreamTest()
         {
             TestRunner runner = new TestRunner(CommonHelper.GetTraceePath(), output);
-            runner.Start(5000);
+            runner.Start(3000);
             DiagnosticsClient client = new DiagnosticsClient(runner.Pid);
             runner.PrintStatus();
             output.WriteLine($"[{DateTime.Now.ToString()}] Trying to start an EventPipe session on process {runner.Pid}");

src/tests/Microsoft.Diagnostics.NETCore.Client/GetPublishedProcessesTests.cs

@@ -48,7 +48,6 @@ public void MultiplePublishedProcessTest()
                 runner[i].Start();
                 pids[i] = runner[i].Pid;
             }
-            System.Threading.Thread.Sleep(2000);
             List<int> publishedProcesses = new List<int>(DiagnosticsClient.GetPublishedProcesses());
             foreach (int p in publishedProcesses)
             {

src/tests/Microsoft.Diagnostics.NETCore.Client/TestRunner.cs

@@ -5,13 +5,17 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
+using System.Linq;
 using System.Threading;
 using Xunit;
 using Xunit.Abstractions;
 
 using Microsoft.Diagnostics.TestHelpers;
 
 using Microsoft.Diagnostics.NETCore.Client;
+using System.Threading.Tasks;
+using System.Runtime.InteropServices;
+using System.IO;
 
 namespace Microsoft.Diagnostics.NETCore.Client
 {
@@ -57,9 +61,30 @@ public void Start(int timeoutInMS=0)
                 outputHelper.WriteLine($"Have total {testProcess.Modules.Count} modules loaded");
             }
 
-            outputHelper.WriteLine($"[{DateTime.Now.ToString()}] Sleeping for {timeoutInMS} ms.");
-            Thread.Sleep(timeoutInMS);
-            outputHelper.WriteLine($"[{DateTime.Now.ToString()}] Done sleeping. Ready to test.");
+            // Block until we see the IPC channel created, or until timeout specified.
+            Task monitorSocketTask = Task.Run(() =>
+            {
+                while (true)
+                {
+                    if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+                    {
+                        // On Windows, namedpipe connection will block until the named pipe is ready to connect so no need to block here
+                        break;
+                    }
+                    else
+                    {
+                        // On Linux, we wait until the socket is created.
+                        var matchingFiles = Directory.GetFiles(Path.GetTempPath(), $"dotnet-diagnostic-{testProcess.Id}-*-socket"); // Try best match.
+                        if (matchingFiles.Length > 0)
+                        {
+                            break;
+                        }
+                    }
+                    Thread.Sleep(100);
+                }
+            });
+
+            monitorSocketTask.Wait(TimeSpan.FromMilliseconds(timeoutInMS));
         }
 
         public void Stop()