Improve test robustness with path validation and named constant

Co-authored-by: TingluoHuang <1750815+TingluoHuang@users.noreply.github.com>

src/Runner.Listener/Runner.cs

@@ -5,8 +5,8 @@ using System.IO;
 using System.Linq;
 using System.Reflection;
 using System.Runtime.CompilerServices;
-using System.Security.Cryptography;
 using System.Security.Claims;
+using System.Security.Cryptography;
 using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
@@ -406,12 +406,27 @@ namespace GitHub.Runner.Listener
             try
             {
                 Trace.Info(nameof(RunAsync));
-                
+
+                // Validate directory permissions.
+                string workDirectory = HostContext.GetDirectory(WellKnownDirectory.Work);
+                Trace.Info($"Validating directory permissions for: '{workDirectory}'");
+                try
+                {
+                    Directory.CreateDirectory(workDirectory);
+                    IOUtil.ValidateExecutePermission(workDirectory);
+                }
+                catch (Exception ex)
+                {
+                    Trace.Error(ex);
+                    _term.WriteError($"Fail to create and validate runner's work directory '{workDirectory}'.");
+                    return Constants.Runner.ReturnCode.TerminatedError;
+                }
+
                 // First try using migrated settings if available
                 var configManager = HostContext.GetService<IConfigurationManager>();
                 RunnerSettings migratedSettings = null;
-                
-                try 
+
+                try
                 {
                     migratedSettings = configManager.LoadMigratedSettings();
                     Trace.Info("Loaded migrated settings from .runner_migrated file");
@@ -422,15 +437,15 @@ namespace GitHub.Runner.Listener
                     // If migrated settings file doesn't exist or can't be loaded, we'll use the provided settings
                     Trace.Info($"Failed to load migrated settings: {ex.Message}");
                 }
-                
+
                 bool usedMigratedSettings = false;
-                
+
                 if (migratedSettings != null)
                 {
                     // Try to create session with migrated settings first
                     Trace.Info("Attempting to create session using migrated settings");
                     _listener = GetMessageListener(migratedSettings, isMigratedSettings: true);
-                    
+
                     try
                     {
                         CreateSessionResult createSessionResult = await _listener.CreateSessionAsync(HostContext.RunnerShutdownToken);
@@ -450,7 +465,7 @@ namespace GitHub.Runner.Listener
                         Trace.Error($"Exception when creating session with migrated settings: {ex}");
                     }
                 }
-                
+
                 // If migrated settings weren't used or session creation failed, use original settings
                 if (!usedMigratedSettings)
                 {
@@ -503,7 +518,7 @@ namespace GitHub.Runner.Listener
                             restartSession = true;
                             break;
                         }
-                        
+
                         TaskAgentMessage message = null;
                         bool skipMessageDeletion = false;
                         try
@@ -859,7 +874,7 @@ namespace GitHub.Runner.Listener
             {
                 restart = false;
                 returnCode = await RunAsync(settings, runOnce);
-                
+
                 if (returnCode == Constants.Runner.ReturnCode.RunnerConfigurationRefreshed)
                 {
                     Trace.Info("Runner configuration was refreshed, restarting session...");

src/Test/L0/Listener/RunnerL0.cs

@@ -1076,5 +1076,75 @@ namespace GitHub.Runner.Common.Tests.Listener
                 Assert.True(hc.AllowAuthMigration);
             }
         }
+
+        [Fact]
+        [Trait("Level", "L0")]
+        [Trait("Category", "Runner")]
+        public async Task RunCommand_ShouldReturnTerminatedError_WhenWorkDirCreationFails()
+        {
+            using (var hostCtx = new TestHostContext(this))
+            {
+                // Setup: arrange mocks and runner instance
+                var runnerInstance = new Runner.Listener.Runner();
+                hostCtx.SetSingleton<IConfigurationManager>(_configurationManager.Object);
+                hostCtx.SetSingleton<IJobNotification>(_jobNotification.Object);
+                hostCtx.SetSingleton<IMessageListener>(_messageListener.Object);
+                hostCtx.SetSingleton<IPromptManager>(_promptManager.Object);
+                hostCtx.SetSingleton<IConfigurationStore>(_configStore.Object);
+                hostCtx.SetSingleton<IRunnerServer>(_runnerServer.Object);
+                hostCtx.EnqueueInstance<IErrorThrottler>(_acquireJobThrottler.Object);
+
+                runnerInstance.Initialize(hostCtx);
+
+                // Create a file at the work directory path to block directory creation
+                string workPath = hostCtx.GetDirectory(WellKnownDirectory.Work);
+
+                // Clean up any existing directory first
+                if (Directory.Exists(workPath))
+                {
+                    Directory.Delete(workPath, recursive: true);
+                }
+
+                // Place a file where the work directory should be - this blocks Directory.CreateDirectory
+                string parentPath = Path.GetDirectoryName(workPath);
+                Assert.NotNull(parentPath);
+                Assert.NotEmpty(parentPath);
+                Directory.CreateDirectory(parentPath);
+
+                const string blockingFileContent = "test file blocking directory creation";
+                File.WriteAllText(workPath, blockingFileContent);
+
+                const int testPoolId = 12345;
+                const int testAgentId = 67890;
+
+                var runnerConfig = new RunnerSettings
+                {
+                    PoolId = testPoolId,
+                    AgentId = testAgentId
+                };
+
+                _configurationManager.Setup(m => m.LoadSettings()).Returns(runnerConfig);
+                _configurationManager.Setup(m => m.IsConfigured()).Returns(true);
+                _configStore.Setup(m => m.IsServiceConfigured()).Returns(false);
+
+                try
+                {
+                    // Execute: run the command which should fail during work dir validation
+                    var cmd = new CommandSettings(hostCtx, new string[] { "run" });
+                    int exitCode = await runnerInstance.ExecuteCommand(cmd);
+
+                    // Verify: should return TerminatedError code when dir creation fails
+                    Assert.Equal(Constants.Runner.ReturnCode.TerminatedError, exitCode);
+                }
+                finally
+                {
+                    // Cleanup: remove the blocking file
+                    if (File.Exists(workPath))
+                    {
+                        File.Delete(workPath);
+                    }
+                }
+            }
+        }
     }
 }