Fix hosting tests not capturing beginning process logs (#27565)

Author: BrennanConroy

src/Hosting/Server.IntegrationTesting/src/Deployers/SelfHostDeployer.cs

@@ -24,6 +24,11 @@ public class SelfHostDeployer : ApplicationDeployer
 
         public Process HostProcess { get; private set; }
 
+        // Use this property before calling DeployAsync
+        // instead of using HostProcess.OutputDataReceived
+        // in order to capture process output from the beginning of the process
+        public Action<string> ProcessOutputListener { get; set; }
+
         public SelfHostDeployer(DeploymentParameters deploymentParameters, ILoggerFactory loggerFactory)
             : base(deploymentParameters, loggerFactory)
         {
@@ -158,6 +163,8 @@ public override async Task<DeploymentResult> DeployAsync()
                             actualUrl = new Uri(m.Groups["url"].Value);
                         }
                     }
+
+                    ProcessOutputListener?.Invoke(dataArgs.Data);
                 };
                 var hostExitTokenSource = new CancellationTokenSource();
                 HostProcess.Exited += (sender, e) =>

src/Hosting/test/FunctionalTests/ShutdownTests.cs

@@ -72,21 +72,20 @@ private async Task ExecuteShutdownTest(string testName, string shutdownMechanic)
 
                 using (var deployer = new SelfHostDeployer(deploymentParameters, loggerFactory))
                 {
-                    await deployer.DeployAsync();
-
                     var startedTcs = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
                     var completedTcs = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
                     var output = string.Empty;
-                    deployer.HostProcess.OutputDataReceived += (sender, args) =>
+
+                    deployer.ProcessOutputListener = (data) =>
                     {
-                        if (!string.IsNullOrEmpty(args.Data) && args.Data.StartsWith(StartedMessage, StringComparison.Ordinal))
+                        if (!string.IsNullOrEmpty(data) && data.StartsWith(StartedMessage, StringComparison.Ordinal))
                         {
                             startedTcs.TrySetResult();
-                            output += args.Data.Substring(StartedMessage.Length) + '\n';
+                            output += data.Substring(StartedMessage.Length) + '\n';
                         }
                         else
                         {
-                            output += args.Data + '\n';
+                            output += data + '\n';
                         }
 
                         if (output.Contains(CompletionMessage))
@@ -95,6 +94,8 @@ private async Task ExecuteShutdownTest(string testName, string shutdownMechanic)
                         }
                     };
 
+                    await deployer.DeployAsync();
+
                     try
                     {
                         await startedTcs.Task.TimeoutAfter(TimeSpan.FromMinutes(1));

src/Hosting/test/FunctionalTests/WebHostBuilderTests.cs

@@ -42,19 +42,20 @@ public async Task InjectedStartup_DefaultApplicationNameIsEntryAssembly(TestVari
 
                 using (var deployer = new SelfHostDeployer(deploymentParameters, loggerFactory))
                 {
-                    await deployer.DeployAsync();
-
-                    string output = string.Empty;
                     var tcs = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
-                    deployer.HostProcess.OutputDataReceived += (sender, args) =>
+                    var output = string.Empty;
+
+                    deployer.ProcessOutputListener = (data) =>
                     {
-                        if (!string.IsNullOrWhiteSpace(args.Data))
+                        if (!string.IsNullOrWhiteSpace(data))
                         {
-                            output += args.Data + '\n';
+                            output += data + '\n';
                             tcs.TrySetResult();
                         }
                     };
 
+                    await deployer.DeployAsync();
+
                     try
                     {
                         await tcs.Task.TimeoutAfter(TimeSpan.FromMinutes(1));