Add --enable-coverage flag for code coverage collection from device tests

src/Microsoft.DotNet.XHarness.Android/InstrumentationRunner.cs

@@ -18,6 +18,7 @@ public class InstrumentationRunner
 
     // nunit2 one should go away eventually
     private static readonly string[] s_xmlOutputVariableNames = { "nunit2-results-path", "test-results-path" };
+    private const string CoverageResultsPathVariableName = "coverage-results-path";
     private const string TestRunSummaryVariableName = "test-execution-summary";
     private const string ShortMessageVariableName = "shortMsg";
     private const string ProcessCrashedShortMessage = "Process crashed";
@@ -129,6 +130,21 @@ public ExitCode RunApkInstrumentation(
         bool failurePullingFiles = PullResultXMLs(apkPackageName, outputDirectory, resultValues)!;
         bool processCrashed = false;
 
+        // Pull coverage results if present (non-fatal on failure)
+        if (resultValues.TryGetValue(CoverageResultsPathVariableName, out string? coveragePath))
+        {
+            _logger.LogInformation($"Found coverage results file: '{coveragePath}'");
+            try
+            {
+                _runner.PullFiles(apkPackageName, coveragePath, outputDirectory);
+                _logger.LogInformation($"Coverage results pulled to '{outputDirectory}'");
+            }
+            catch (Exception toLog)
+            {
+                _logger.LogWarning(toLog, "Failed to pull coverage results from {filePathOnDevice}. Coverage data may be unavailable.", coveragePath);
+            }
+        }
+
         if (resultValues.TryGetValue(TestRunSummaryVariableName, out string? testRunSummary))
         {
             _logger.LogInformation($"Test execution summary:{Environment.NewLine}{testRunSummary}");

src/Microsoft.DotNet.XHarness.CLI/CommandArguments/Android/AndroidRunCommandArguments.cs

@@ -20,6 +20,7 @@ internal class AndroidRunCommandArguments : XHarnessCommandArguments, IAndroidAp
     public ExpectedExitCodeArgument ExpectedExitCode { get; } = new((int)Common.CLI.ExitCode.SUCCESS);
     public DeviceOutputFolderArgument DeviceOutputFolder { get; } = new();
     public WifiArgument Wifi { get; } = new();
+    public CommandArguments.EnableCoverageArgument EnableCoverage { get; } = new();
 
     protected override IEnumerable<Argument> GetArguments() => new Argument[]
     {
@@ -34,5 +35,6 @@ internal class AndroidRunCommandArguments : XHarnessCommandArguments, IAndroidAp
         ExpectedExitCode,
         DeviceOutputFolder,
         Wifi,
+        EnableCoverage,
     };
 }

src/Microsoft.DotNet.XHarness.CLI/CommandArguments/Android/AndroidTestCommandArguments.cs

@@ -23,6 +23,7 @@ internal class AndroidTestCommandArguments : XHarnessCommandArguments, IAndroidA
     public ExpectedExitCodeArgument ExpectedExitCode { get; } = new((int)Common.CLI.ExitCode.SUCCESS);
     public DeviceOutputFolderArgument DeviceOutputFolder { get; } = new();
     public WifiArgument Wifi { get; } = new();
+    public CommandArguments.EnableCoverageArgument EnableCoverage { get; } = new();
 
     protected override IEnumerable<Argument> GetArguments() => new Argument[]
     {
@@ -39,6 +40,7 @@ internal class AndroidTestCommandArguments : XHarnessCommandArguments, IAndroidA
         ExpectedExitCode,
         DeviceOutputFolder,
         Wifi,
+        EnableCoverage,
     };
 
     public override void Validate()

src/Microsoft.DotNet.XHarness.CLI/CommandArguments/Apple/AppleJustTestCommandArguments.cs

@@ -26,6 +26,7 @@ internal class AppleJustTestCommandArguments : XHarnessCommandArguments, IAppleA
     public EnableLldbArgument EnableLldb { get; } = new();
     public EnvironmentalVariablesArgument EnvironmentalVariables { get; } = new();
     public SignalAppEndArgument SignalAppEnd { get; } = new();
+    public CommandArguments.EnableCoverageArgument EnableCoverage { get; } = new();
 
     protected override IEnumerable<Argument> GetArguments() => new Argument[]
     {
@@ -45,6 +46,7 @@ internal class AppleJustTestCommandArguments : XHarnessCommandArguments, IAppleA
         EnableLldb,
         SignalAppEnd,
         EnvironmentalVariables,
+        EnableCoverage,
     };
 
     public override void Validate()

src/Microsoft.DotNet.XHarness.CLI/CommandArguments/Apple/AppleTestCommandArguments.cs

@@ -26,6 +26,7 @@ internal class AppleTestCommandArguments : XHarnessCommandArguments, IAppleAppRu
     public EnvironmentalVariablesArgument EnvironmentalVariables { get; } = new();
     public ResetSimulatorArgument ResetSimulator { get; } = new();
     public SignalAppEndArgument SignalAppEnd { get; } = new();
+    public CommandArguments.EnableCoverageArgument EnableCoverage { get; } = new();
 
     protected override IEnumerable<Argument> GetArguments() => new Argument[]
     {
@@ -46,5 +47,6 @@ internal class AppleTestCommandArguments : XHarnessCommandArguments, IAppleAppRu
         SignalAppEnd,
         EnvironmentalVariables,
         ResetSimulator,
+        EnableCoverage,
     };
 }

src/Microsoft.DotNet.XHarness.CLI/CommandArguments/Arguments/EnableCoverageArgument.cs

@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Microsoft.DotNet.XHarness.CLI.CommandArguments;
+
+/// <summary>
+/// Shared --enable-coverage switch used across all platforms (Android, Apple, WASM).
+/// </summary>
+internal class EnableCoverageArgument : SwitchArgument
+{
+    public EnableCoverageArgument() : base("enable-coverage", "Enable code coverage collection during test execution", false)
+    {
+    }
+}

src/Microsoft.DotNet.XHarness.CLI/CommandArguments/WASM/WasmTestBrowserCommandArguments.cs

@@ -40,6 +40,7 @@ internal class WasmTestBrowserCommandArguments : XHarnessCommandArguments, IWebS
     public WebServerUseDefaultFilesArguments WebServerUseDefaultFiles { get; } = new();
     public WebServerUploadResults WebServerUploadResults { get; } = new();
     public bool IsWebServerEnabled => WebServerMiddlewarePathsAndTypes.Value.Count > 0;
+    public CommandArguments.EnableCoverageArgument EnableCoverage { get; } = new();
 
     protected override IEnumerable<Argument> GetArguments() => new Argument[]
     {
@@ -69,6 +70,7 @@ internal class WasmTestBrowserCommandArguments : XHarnessCommandArguments, IWebS
             WebServerUseCors,
             WebServerUseCrossOriginPolicy,
             WebServerUseDefaultFiles,
+            EnableCoverage,
     };
 
     public override void Validate()

src/Microsoft.DotNet.XHarness.CLI/CommandArguments/WASM/WasmTestCommandArguments.cs

@@ -32,6 +32,7 @@ internal class WasmTestCommandArguments : XHarnessCommandArguments, IWebServerAr
     public WebServerUseDefaultFilesArguments WebServerUseDefaultFiles { get; } = new();
     public WebServerUploadResults WebServerUploadResults { get; } = new();
     public bool IsWebServerEnabled => WebServerMiddlewarePathsAndTypes.Value.Count > 0;
+    public CommandArguments.EnableCoverageArgument EnableCoverage { get; } = new();
 
     protected override IEnumerable<Argument> GetArguments() => new Argument[]
     {
@@ -55,5 +56,6 @@ internal class WasmTestCommandArguments : XHarnessCommandArguments, IWebServerAr
             WebServerUseCors,
             WebServerUseCrossOriginPolicy,
             WebServerUseDefaultFiles,
+            EnableCoverage,
     };
 }

src/Microsoft.DotNet.XHarness.CLI/Commands/Android/AndroidRunCommand.cs

@@ -79,6 +79,11 @@ protected override ExitCode InvokeCommand(ILogger logger)
             runner.EnableWifi(Arguments.Wifi == WifiStatus.Enable);
         }
 
+        if (Arguments.EnableCoverage)
+        {
+            Arguments.InstrumentationArguments.Value["enable-coverage"] = "true";
+        }
+
         var instrumentationRunner = new InstrumentationRunner(logger, runner);
         return instrumentationRunner.RunApkInstrumentation(
             Arguments.PackageName,

src/Microsoft.DotNet.XHarness.CLI/Commands/Android/AndroidTestCommand.cs

@@ -61,6 +61,11 @@ protected override ExitCode InvokeCommand(ILogger logger)
             {
                 runner.ClearAdbLog();
 
+                if (Arguments.EnableCoverage)
+                {
+                    Arguments.InstrumentationArguments.Value["enable-coverage"] = "true";
+                }
+
                 var instrumentationRunner = new InstrumentationRunner(logger, runner);
                 exitCode = instrumentationRunner.RunApkInstrumentation(
                     Arguments.PackageName,

src/Microsoft.DotNet.XHarness.CLI/Commands/Apple/AppleJustTestCommand.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System.Collections.Generic;
+using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.DotNet.XHarness.Apple;
@@ -23,8 +25,21 @@ public AppleJustTestCommand(IServiceCollection services) : base("just-test", fal
     {
     }
 
-    protected override Task<ExitCode> InvokeInternal(ServiceProvider serviceProvider, CancellationToken cancellationToken) =>
-        serviceProvider.GetRequiredService<IJustTestOrchestrator>()
+    protected override Task<ExitCode> InvokeInternal(ServiceProvider serviceProvider, CancellationToken cancellationToken)
+    {
+        var envVars = Arguments.EnvironmentalVariables.Value;
+
+        if (Arguments.EnableCoverage)
+        {
+            var coverageVars = new List<(string, string)>(envVars)
+            {
+                ("NUNIT_ENABLE_COVERAGE", "true"),
+                ("NUNIT_COVERAGE_OUTPUT_PATH", "coverage.cobertura.xml"),
+            };
+            envVars = coverageVars;
+        }
+
+        return serviceProvider.GetRequiredService<IJustTestOrchestrator>()
             .OrchestrateTest(
                 Arguments.BundleIdentifier,
                 Arguments.Target,
@@ -38,7 +53,8 @@ protected override Task<ExitCode> InvokeInternal(ServiceProvider serviceProvider
                 includeWirelessDevices: Arguments.IncludeWireless,
                 enableLldb: Arguments.EnableLldb,
                 signalAppEnd: Arguments.SignalAppEnd,
-                Arguments.EnvironmentalVariables.Value,
+                envVars,
                 PassThroughArguments,
                 cancellationToken);
+    }
 }

src/Microsoft.DotNet.XHarness.CLI/Commands/Apple/AppleTestCommand.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System.Collections.Generic;
+using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.DotNet.XHarness.Apple;
@@ -25,8 +27,24 @@ public AppleTestCommand(IServiceCollection services) : base("test", false, servi
     {
     }
 
-    protected override Task<ExitCode> InvokeInternal(ServiceProvider serviceProvider, CancellationToken cancellationToken) =>
-        serviceProvider.GetRequiredService<ITestOrchestrator>()
+    protected override Task<ExitCode> InvokeInternal(ServiceProvider serviceProvider, CancellationToken cancellationToken)
+    {
+        var envVars = Arguments.EnvironmentalVariables.Value;
+
+        if (Arguments.EnableCoverage)
+        {
+            // Inject coverage env vars so the test runner on the device enables coverage.
+            // Use Documents/coverage.cobertura.xml — the same directory where test results go,
+            // which the orchestrator already knows how to pull from the app container.
+            var coverageVars = new List<(string, string)>(envVars)
+            {
+                ("NUNIT_ENABLE_COVERAGE", "true"),
+                ("NUNIT_COVERAGE_OUTPUT_PATH", "coverage.cobertura.xml"),
+            };
+            envVars = coverageVars;
+        }
+
+        return serviceProvider.GetRequiredService<ITestOrchestrator>()
             .OrchestrateTest(
                 Arguments.AppBundlePath,
                 Arguments.Target,
@@ -41,7 +59,8 @@ protected override Task<ExitCode> InvokeInternal(ServiceProvider serviceProvider
                 resetSimulator: Arguments.ResetSimulator,
                 enableLldb: Arguments.EnableLldb,
                 signalAppEnd: Arguments.SignalAppEnd,
-                Arguments.EnvironmentalVariables.Value,
+                envVars,
                 PassThroughArguments,
                 cancellationToken);
+    }
 }

src/Microsoft.DotNet.XHarness.CLI/Commands/WASM/Browser/WasmTestBrowserCommand.cs

@@ -53,11 +53,16 @@ protected override async Task<ExitCode> InvokeInternal(ILogger logger)
         var serviceProvider = Services.BuildServiceProvider();
         var diagnosticsData = serviceProvider.GetRequiredService<IDiagnosticsData>();
 
+        var coverageOutputPath = Arguments.EnableCoverage
+            ? Path.Combine(Arguments.OutputDirectory, "coverage.cobertura.xml")
+            : null;
+
         var logProcessor = new WasmTestMessagesProcessor(xmlResultsFilePath,
                                                          stdoutFilePath,
                                                          logger,
                                                          Arguments.ErrorPatternsFile,
-                                                         symbolicator);
+                                                         symbolicator,
+                                                         coverageOutputPath);
         var runner = new WasmBrowserTestRunner(
                             Arguments,
                             PassThroughArguments,

src/Microsoft.DotNet.XHarness.CLI/Commands/WASM/JS/WasmTestCommand.cs

@@ -128,11 +128,16 @@ protected override async Task<ExitCode> InvokeInternal(ILogger logger)
                                                            Arguments.SymbolicatePatternsFileArgument,
                                                            logger);
 
+            var coverageOutputPath = Arguments.EnableCoverage
+                ? Path.Combine(Arguments.OutputDirectory, "coverage.cobertura.xml")
+                : null;
+
             var logProcessor = new WasmTestMessagesProcessor(xmlResultsFilePath,
                                                              stdoutFilePath,
                                                              logger,
                                                              Arguments.ErrorPatternsFile,
-                                                             symbolicator);
+                                                             symbolicator,
+                                                             coverageOutputPath);
             var logProcessorTask = Task.Run(() => logProcessor.RunAsync(cts.Token));
 
             var processTask = processManager.ExecuteCommandAsync(

src/Microsoft.DotNet.XHarness.CLI/Commands/WASM/WasmTestMessagesProcessor.cs

@@ -19,8 +19,10 @@ namespace Microsoft.DotNet.XHarness.CLI.Commands.Wasm;
 public class WasmTestMessagesProcessor
 {
     private static Regex xmlRx = new Regex(@"^STARTRESULTXML ([0-9]*) ([^ ]*) ENDRESULTXML", RegexOptions.Compiled | RegexOptions.CultureInvariant);
+    private static Regex coverageRx = new Regex(@"^STARTCOVERAGEXML ([0-9]*) ([^ ]*) ENDCOVERAGEXML", RegexOptions.Compiled | RegexOptions.CultureInvariant);
     private readonly StreamWriter _stdoutFileWriter;
     private readonly string _xmlResultsFilePath;
+    private readonly string? _coverageOutputPath;
     private static TimeSpan s_logMessagesTimeout = TimeSpan.FromMinutes(2);
 
     private readonly ILogger _logger;
@@ -38,9 +40,10 @@ public class WasmTestMessagesProcessor
     public TaskCompletionSource WasmExitReceivedTcs { get; } = new ();
     public int? ForwardedExitCode {get; private set; }
 
-    public WasmTestMessagesProcessor(string xmlResultsFilePath, string stdoutFilePath, ILogger logger, string? errorPatternsFile = null, WasmSymbolicatorBase? symbolicator = null)
+    public WasmTestMessagesProcessor(string xmlResultsFilePath, string stdoutFilePath, ILogger logger, string? errorPatternsFile = null, WasmSymbolicatorBase? symbolicator = null, string? coverageOutputPath = null)
     {
         _xmlResultsFilePath = xmlResultsFilePath;
+        _coverageOutputPath = coverageOutputPath;
         _stdoutFileWriter = File.CreateText(stdoutFilePath);
         _stdoutFileWriter.AutoFlush = true;
         _logger = logger;
@@ -184,6 +187,7 @@ private void ProcessMessage(string message, bool isError = false)
         line = line.TrimEnd();
 
         var match = xmlRx.Match(line);
+        var coverageMatch = coverageRx.Match(line);
         if (match.Success)
         {
             var expectedLength = Int32.Parse(match.Groups[1].Value);
@@ -201,6 +205,26 @@ private void ProcessMessage(string message, bool isError = false)
                 }
             }
         }
+        else if (coverageMatch.Success && _coverageOutputPath != null)
+        {
+            var expectedLength = Int32.Parse(coverageMatch.Groups[1].Value);
+            var bytes = System.Convert.FromBase64String(coverageMatch.Groups[2].Value);
+            var outputDir = Path.GetDirectoryName(_coverageOutputPath);
+            if (!string.IsNullOrEmpty(outputDir) && !Directory.Exists(outputDir))
+            {
+                Directory.CreateDirectory(outputDir);
+            }
+
+            File.WriteAllBytes(_coverageOutputPath, bytes);
+            if (bytes.Length == expectedLength)
+            {
+                _logger.LogInformation($"Received expected {bytes.Length} bytes of coverage data, saved to {_coverageOutputPath}");
+            }
+            else
+            {
+                _logger.LogWarning($"Received {bytes.Length} bytes of coverage data but expected {expectedLength}, saved to {_coverageOutputPath}");
+            }
+        }
         else
         {
             ScanMessageForErrorPatterns(line);

src/Microsoft.DotNet.XHarness.TestRunners.Common/AndroidApplicationEntryPointBase.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System;
 using System.IO;
 using System.Threading.Tasks;
 
@@ -28,5 +29,12 @@ public override async Task RunAsync()
         var options = ApplicationOptions.Current;
         using TextWriter? resultsFileMaybe = options.EnableXml ? File.CreateText(TestsResultsFinalPath) : null;
         await InternalRunAsync(options, Logger, resultsFileMaybe);
+
+        if (CoverageResultPath != null)
+        {
+            // Report the coverage path via stdout so the Instrumentation class can
+            // forward it as INSTRUMENTATION_RESULT: coverage-results-path=<path>
+            Console.WriteLine($"INSTRUMENTATION_RESULT: coverage-results-path={CoverageResultPath}");
+        }
     }
 }