Add retry logic to stabilize flaky UI tests

tests/E2E Tests/WebAppUiTests/B2CWebAppCallsWebApiLocally.cs

@@ -42,7 +42,7 @@ public B2CWebAppCallsWebApiLocally(ITestOutputHelper output)
 
         [Fact]
         [SupportedOSPlatform("windows")]
-        public async Task Susi_B2C_LocalAccount_TodoAppFucntionsCorrectlyAsync()
+        public async Task Susi_B2C_LocalAccount_TodoAppFunctionsCorrectlyAsync()
         {
             // Web app and api environmental variable setup.
             DefaultAzureCredential azureCred = new();
@@ -79,9 +79,9 @@ public async Task Susi_B2C_LocalAccount_TodoAppFucntionsCorrectlyAsync()
                 // The delay before starting client prevents transient devbox issue where the client fails to load the first time after rebuilding.
                 serviceProcess = UiTestHelpers.StartProcessLocally(_testAssemblyPath, _devAppPath + TC.s_todoListServicePath, TC.s_todoListServiceExe, serviceEnvVars);
                 await Task.Delay(3000);
-                clientProcess = UiTestHelpers.StartProcessLocally(_testAssemblyPath, _devAppPath + TC.s_todoListClientPath, TC.s_todoListClientExe, clientEnvVars);
+                clientProcess = UiTestHelpers.StartProcessLocally(_testAssemblyPath, _devAppPath + TC.s_todoListClientPath, TC.s_todoListClientExe, clientEnvVars, 5);
 
-                if (!UiTestHelpers.ProcessesAreAlive(new List<Process>() { clientProcess, serviceProcess }))
+                if (!UiTestHelpers.ProcessesAreAlive([clientProcess, serviceProcess]))
                 {
                     Assert.Fail(TC.WebAppCrashedString);
                 }

tests/E2E Tests/WebAppUiTests/UiTestHelpers.cs

@@ -142,8 +142,13 @@ await page.Context.Tracing.StartAsync(new()
         /// <param name="executableName">The name of the executable that launches the process.</param>
         /// <param name="portNumber">The port for the process to listen on.</param>
         /// <param name="isHttp">If the launch URL is http or https. Default is https.</param>
+        /// <param name="maxRetries">Optionally, maximum number of retries if the process exited prematurely.</param>
         /// <returns>The started process.</returns>
-        public static Process StartProcessLocally(string testAssemblyLocation, string appLocation, string executableName, Dictionary<string, string>? environmentVariables = null)
+        public static Process StartProcessLocally(
+            string testAssemblyLocation,
+            string appLocation, string executableName,
+            Dictionary<string, string>? environmentVariables = null,
+            int maxRetries = 0)
         {
             string applicationWorkingDirectory = GetApplicationWorkingDirectory(testAssemblyLocation, appLocation);
             ProcessStartInfo processStartInfo = new ProcessStartInfo(applicationWorkingDirectory + executableName)
@@ -161,14 +166,27 @@ public static Process StartProcessLocally(string testAssemblyLocation, string ap
                 }
             }
 
-            Process? process = Process.Start(processStartInfo);
+            var currentAttempt = 1;
+            Process? process;
+            do
+            {
+                Thread.Sleep(1000 * currentAttempt++); // Exponential backoff
+                process = Process.Start(processStartInfo);
+            } while (currentAttempt++ <= maxRetries && ProcessIsAlive(process));
 
             if (process == null)
             {
                 throw new Exception($"Could not start process {executableName}");
             }
             else
             {
+                // Log the output and error streams
+                process.OutputDataReceived += (sender, e) => Console.WriteLine(e.Data);
+                process.ErrorDataReceived += (sender, e) => Console.Error.WriteLine(e.Data);
+
+                process.BeginOutputReadLine();
+                process.BeginErrorReadLine();
+
                 return process;
             }
         }
@@ -275,9 +293,9 @@ public static bool ProcessesAreAlive(List<Process> processes)
         /// </summary>
         /// <param name="process">Process to check</param>
         /// <returns>True if alive false if not</returns>
-        public static bool ProcessIsAlive(Process process)
+        public static bool ProcessIsAlive(Process? process)
         {
-            return !process.HasExited;
+            return process != null && !process.HasExited;
         }
 
         /// <summary>