Report PID-qualified testhost controller pipe env var

src/Platform/Microsoft.Testing.Platform/Hosts/TestHostBuilder.Utilities.cs

@@ -38,7 +38,7 @@ internal sealed partial class TestHostBuilder
         }
 
         string pipeEnvironmentVariable = $"{EnvironmentVariableConstants.TESTINGPLATFORM_TESTHOSTCONTROLLER_PIPENAME}_{testHostControllerInfo.GetTestHostControllerPID()}";
-        string pipeName = environment.GetEnvironmentVariable(pipeEnvironmentVariable) ?? throw new InvalidOperationException($"Unexpected null pipe name from environment variable '{EnvironmentVariableConstants.TESTINGPLATFORM_TESTHOSTCONTROLLER_PIPENAME}'");
+        string pipeName = environment.GetEnvironmentVariable(pipeEnvironmentVariable) ?? throw new InvalidOperationException($"Unexpected null pipe name from environment variable '{pipeEnvironmentVariable}'");
 
         environment.SetEnvironmentVariable(pipeEnvironmentVariable, string.Empty);
 

test/UnitTests/Microsoft.Testing.Platform.UnitTests/TestHostBuilderTests.cs

@@ -0,0 +1,58 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using Microsoft.Testing.Platform.CommandLine;
+using Microsoft.Testing.Platform.Configurations;
+using Microsoft.Testing.Platform.Helpers;
+using Microsoft.Testing.Platform.Hosts;
+using Microsoft.Testing.Platform.Logging;
+using Microsoft.Testing.Platform.Services;
+using Microsoft.Testing.Platform.TestHostControllers;
+
+namespace Microsoft.Testing.Platform.UnitTests;
+
+[TestClass]
+[UnsupportedOSPlatform("browser")]
+public sealed class TestHostBuilderTests
+{
+    [TestMethod]
+    public async Task ConnectToTestHostProcessMonitorIfAvailableAsync_MissingPipeName_ReportsPidQualifiedEnvironmentVariable()
+    {
+        const int testHostControllerPid = 123456789;
+        string pipeEnvironmentVariable = $"{EnvironmentVariableConstants.TESTINGPLATFORM_TESTHOSTCONTROLLER_PIPENAME}_{testHostControllerPid}";
+        SystemEnvironment environment = new();
+        string? previousPipeName = environment.GetEnvironmentVariable(pipeEnvironmentVariable);
+        environment.SetEnvironmentVariable(pipeEnvironmentVariable, null);
+
+        try
+        {
+            MethodInfo method = typeof(TestHostBuilder).GetMethod("ConnectToTestHostProcessMonitorIfAvailableAsync", BindingFlags.NonPublic | BindingFlags.Static)!;
+            TestHostControllerInfo testHostControllerInfo = new(new CommandLineParseResult(
+                null,
+                [new CommandLineParseOption(PlatformCommandLineProvider.TestHostControllerPIDOptionKey, [testHostControllerPid.ToString(CultureInfo.InvariantCulture)])],
+                []));
+            CurrentTestApplicationModuleInfo testApplicationModuleInfo = new(environment, new SystemProcessHandler());
+            AggregatedConfiguration configuration = new([], testApplicationModuleInfo, new SystemFileSystem(), environment, new(null, [], []));
+
+            InvalidOperationException exception = await Assert.ThrowsExactlyAsync<InvalidOperationException>(
+                () => ConnectToTestHostProcessMonitorIfAvailableAsync(method, testHostControllerInfo, configuration, environment));
+
+            Assert.AreEqual($"Unexpected null pipe name from environment variable '{pipeEnvironmentVariable}'", exception.Message);
+        }
+        finally
+        {
+            environment.SetEnvironmentVariable(pipeEnvironmentVariable, previousPipeName);
+        }
+    }
+
+    private static async Task ConnectToTestHostProcessMonitorIfAvailableAsync(
+        MethodInfo method,
+        TestHostControllerInfo testHostControllerInfo,
+        AggregatedConfiguration configuration,
+        SystemEnvironment environment)
+    {
+        using CTRLPlusCCancellationTokenSource cancellationTokenSource = new();
+        var connectTask = (Task)method.Invoke(null, [cancellationTokenSource, new NopLogger(), testHostControllerInfo, configuration, environment])!;
+        await connectTask;
+    }
+}