Wait for Function host to fully start in Integration tests (#222)

* Wait for function host to fully start

* Remove unused

* Add logging

* Use different string

* Remove duplicate log

Author: Charles-Gagnon

test/Integration/IntegrationTestBase.cs

@@ -11,7 +11,6 @@
 using System.Reflection;
 using System.Runtime.InteropServices;
 using System.Text;
-using System.Threading;
 using System.Threading.Tasks;
 using Xunit;
 using Xunit.Abstractions;
@@ -189,7 +188,19 @@ protected void StartFunctionHost(string functionName, bool useTestFolder = false
             this.FunctionHost.BeginOutputReadLine();
             this.FunctionHost.BeginErrorReadLine();
 
-            Thread.Sleep(10000);     // This is just to give some time to func host to start, maybe there's a better way to do this (check if port's open?)
+            var taskCompletionSource = new TaskCompletionSource<bool>();
+            this.FunctionHost.OutputDataReceived += (object sender, DataReceivedEventArgs e) =>
+            {
+                // This string is printed after the function host is started up - use this to ensure that we wait long enough
+                // since sometimes the host can take a little while to fully start up
+                if (e.Data.Contains("Job host started"))
+                {
+                    taskCompletionSource.SetResult(true);
+                }
+            };
+            this.TestOutput.WriteLine($"Waiting for Azure Function host to start...");
+            taskCompletionSource.Task.Wait();
+            this.TestOutput.WriteLine($"Azure Function host started!");
         }
 
         private static string GetFunctionsCoreToolsPath()