Apply [StackTraceHidden] to Assert/CollectionAssert/StringAssert (#8277)

src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/AzureDevOpsReporter.cs

@@ -258,7 +258,7 @@ private async Task WriteExceptionAsync(string testDisplayName, string testName,
                     logger.LogTrace($"Using relative path '{relativePath}'.");
                 }
             }
-            else if (file.StartsWith(repoRoot, StringComparison.CurrentCultureIgnoreCase))
+            else if (file.StartsWith(repoRoot, StringComparison.OrdinalIgnoreCase))
             {
                 if (logger.IsEnabled(LogLevel.Trace))
                 {

src/TestFramework/TestFramework/Assertions/Assert.AreEqual.InterpolatedStringHandlers.cs

@@ -12,6 +12,7 @@ namespace Microsoft.VisualStudio.TestTools.UnitTesting;
 /// </summary>
 public sealed partial class Assert
 {
+    [StackTraceHidden]
     [InterpolatedStringHandler]
     [EditorBrowsable(EditorBrowsableState.Never)]
 #pragma warning disable CS1591 // Missing XML comment for publicly visible type or member
@@ -86,6 +87,7 @@ internal void ComputeAssertion(string expectedExpression, string actualExpressio
 #pragma warning restore RS0027 // API with optional parameter(s) should have the most parameters amongst its public overloads
     }
 
+    [StackTraceHidden]
     [InterpolatedStringHandler]
     [EditorBrowsable(EditorBrowsableState.Never)]
     public readonly struct AssertAreNotEqualInterpolatedStringHandler<TArgument>
@@ -152,6 +154,7 @@ internal void ComputeAssertion(string notExpectedExpression, string actualExpres
 #pragma warning restore RS0027 // API with optional parameter(s) should have the most parameters amongst its public overloads
     }
 
+    [StackTraceHidden]
     [InterpolatedStringHandler]
     [EditorBrowsable(EditorBrowsableState.Never)]
     public readonly struct AssertNonGenericAreEqualInterpolatedStringHandler
@@ -263,6 +266,7 @@ internal void ComputeAssertion(string expectedExpression, string actualExpressio
 #pragma warning restore RS0027 // API with optional parameter(s) should have the most parameters amongst its public overloads
     }
 
+    [StackTraceHidden]
     [InterpolatedStringHandler]
     [EditorBrowsable(EditorBrowsableState.Never)]
     public readonly struct AssertNonGenericAreNotEqualInterpolatedStringHandler

src/TestFramework/TestFramework/Assertions/Assert.AreSame.cs

@@ -14,6 +14,7 @@ namespace Microsoft.VisualStudio.TestTools.UnitTesting;
 /// </summary>
 public sealed partial class Assert
 {
+    [StackTraceHidden]
     [InterpolatedStringHandler]
     [EditorBrowsable(EditorBrowsableState.Never)]
 #pragma warning disable CS1591 // Missing XML comment for publicly visible type or member
@@ -74,6 +75,7 @@ internal void ComputeAssertion(string expectedExpression, string actualExpressio
 #pragma warning restore RS0027 // API with optional parameter(s) should have the most parameters amongst its public overloads
     }
 
+    [StackTraceHidden]
     [InterpolatedStringHandler]
     [EditorBrowsable(EditorBrowsableState.Never)]
     public readonly struct AssertAreNotSameInterpolatedStringHandler<TArgument>

src/TestFramework/TestFramework/Assertions/Assert.Contains.cs

@@ -12,6 +12,7 @@ namespace Microsoft.VisualStudio.TestTools.UnitTesting;
 /// </summary>
 public sealed partial class Assert
 {
+    [StackTraceHidden]
     [InterpolatedStringHandler]
     [EditorBrowsable(EditorBrowsableState.Never)]
 #pragma warning disable CS1591 // Missing XML comment for publicly visible type or member

src/TestFramework/TestFramework/Assertions/Assert.Count.cs

@@ -12,6 +12,7 @@ namespace Microsoft.VisualStudio.TestTools.UnitTesting;
 /// </summary>
 public sealed partial class Assert
 {
+    [StackTraceHidden]
     [InterpolatedStringHandler]
     [EditorBrowsable(EditorBrowsableState.Never)]
 #pragma warning disable CS1591 // Missing XML comment for publicly visible type or member
@@ -95,6 +96,7 @@ public void AppendFormatted(object? value, int alignment = 0, string? format = n
 #pragma warning restore RS0027 // API with optional parameter(s) should have the most parameters amongst its public overloads
     }
 
+    [StackTraceHidden]
     [InterpolatedStringHandler]
     [EditorBrowsable(EditorBrowsableState.Never)]
     public readonly struct AssertIsNotEmptyInterpolatedStringHandler<TItem>

src/TestFramework/TestFramework/Assertions/Assert.IsExactInstanceOfType.cs

@@ -14,6 +14,7 @@ namespace Microsoft.VisualStudio.TestTools.UnitTesting;
 /// </summary>
 public sealed partial class Assert
 {
+    [StackTraceHidden]
     [InterpolatedStringHandler]
     [EditorBrowsable(EditorBrowsableState.Never)]
 #pragma warning disable CS1591 // Missing XML comment for publicly visible type or member
@@ -76,6 +77,7 @@ internal void ComputeAssertion(string valueExpression)
 #pragma warning restore RS0027 // API with optional parameter(s) should have the most parameters amongst its public overloads
     }
 
+    [StackTraceHidden]
     [InterpolatedStringHandler]
     [EditorBrowsable(EditorBrowsableState.Never)]
     public readonly struct AssertGenericIsExactInstanceOfTypeInterpolatedStringHandler<TArg>
@@ -135,6 +137,7 @@ internal void ComputeAssertion(string valueExpression)
 #pragma warning restore RS0027 // API with optional parameter(s) should have the most parameters amongst its public overloads
     }
 
+    [StackTraceHidden]
     [InterpolatedStringHandler]
     [EditorBrowsable(EditorBrowsableState.Never)]
     public readonly struct AssertIsNotExactInstanceOfTypeInterpolatedStringHandler
@@ -196,6 +199,7 @@ internal void ComputeAssertion(string valueExpression)
 #pragma warning restore RS0027 // API with optional parameter(s) should have the most parameters amongst its public overloads
     }
 
+    [StackTraceHidden]
     [InterpolatedStringHandler]
     [EditorBrowsable(EditorBrowsableState.Never)]
     public readonly struct AssertGenericIsNotExactInstanceOfTypeInterpolatedStringHandler<TArg>

src/TestFramework/TestFramework/Assertions/Assert.IsInstanceOfType.cs

@@ -14,6 +14,7 @@ namespace Microsoft.VisualStudio.TestTools.UnitTesting;
 /// </summary>
 public sealed partial class Assert
 {
+    [StackTraceHidden]
     [InterpolatedStringHandler]
     [EditorBrowsable(EditorBrowsableState.Never)]
 #pragma warning disable CS1591 // Missing XML comment for publicly visible type or member
@@ -76,6 +77,7 @@ internal void ComputeAssertion(string valueExpression)
 #pragma warning restore RS0027 // API with optional parameter(s) should have the most parameters amongst its public overloads
     }
 
+    [StackTraceHidden]
     [InterpolatedStringHandler]
     [EditorBrowsable(EditorBrowsableState.Never)]
     public readonly struct AssertGenericIsInstanceOfTypeInterpolatedStringHandler<TArg>
@@ -135,6 +137,7 @@ internal void ComputeAssertion(string valueExpression)
 #pragma warning restore RS0027 // API with optional parameter(s) should have the most parameters amongst its public overloads
     }
 
+    [StackTraceHidden]
     [InterpolatedStringHandler]
     [EditorBrowsable(EditorBrowsableState.Never)]
     public readonly struct AssertIsNotInstanceOfTypeInterpolatedStringHandler
@@ -196,6 +199,7 @@ internal void ComputeAssertion(string valueExpression)
 #pragma warning restore RS0027 // API with optional parameter(s) should have the most parameters amongst its public overloads
     }
 
+    [StackTraceHidden]
     [InterpolatedStringHandler]
     [EditorBrowsable(EditorBrowsableState.Never)]
     public readonly struct AssertGenericIsNotInstanceOfTypeInterpolatedStringHandler<TArg>

src/TestFramework/TestFramework/Assertions/Assert.IsNull.cs

@@ -16,6 +16,7 @@ namespace Microsoft.VisualStudio.TestTools.UnitTesting;
 
 public sealed partial class Assert
 {
+    [StackTraceHidden]
     [InterpolatedStringHandler]
     [EditorBrowsable(EditorBrowsableState.Never)]
 #pragma warning disable CS1591 // Missing XML comment for publicly visible type or member
@@ -71,6 +72,7 @@ internal void ComputeAssertion(string valueExpression)
     }
 #pragma warning restore CS1591 // Missing XML comment for publicly visible type or member
 
+    [StackTraceHidden]
     [InterpolatedStringHandler]
     [EditorBrowsable(EditorBrowsableState.Never)]
 #pragma warning disable CS1591 // Missing XML comment for publicly visible type or member

src/TestFramework/TestFramework/Assertions/Assert.IsTrue.cs

@@ -16,6 +16,7 @@ namespace Microsoft.VisualStudio.TestTools.UnitTesting;
 
 public sealed partial class Assert
 {
+    [StackTraceHidden]
     [InterpolatedStringHandler]
     [EditorBrowsable(EditorBrowsableState.Never)]
 #pragma warning disable CS1591 // Missing XML comment for publicly visible type or member
@@ -70,6 +71,7 @@ internal void ComputeAssertion(string conditionExpression)
         public void AppendFormatted(object? value, int alignment = 0, string? format = null) => _builder!.AppendFormat(null, $"{{0,{alignment}:{format}}}", value);
     }
 
+    [StackTraceHidden]
     [InterpolatedStringHandler]
     [EditorBrowsable(EditorBrowsableState.Never)]
     public readonly struct AssertIsFalseInterpolatedStringHandler

src/TestFramework/TestFramework/Assertions/Assert.That.cs

@@ -8,6 +8,7 @@ namespace Microsoft.VisualStudio.TestTools.UnitTesting;
 /// <summary>
 /// Provides That extension to Assert class.
 /// </summary>
+[StackTraceHidden]
 public static partial class AssertExtensions
 {
     // Constants for standardized display values

src/TestFramework/TestFramework/Assertions/Assert.ThrowsException.cs

@@ -14,6 +14,7 @@ namespace Microsoft.VisualStudio.TestTools.UnitTesting;
 /// </summary>
 public sealed partial class Assert
 {
+    [StackTraceHidden]
     [InterpolatedStringHandler]
     [EditorBrowsable(EditorBrowsableState.Never)]
 #pragma warning disable CS1591 // Missing XML comment for publicly visible type or member
@@ -85,6 +86,7 @@ internal TException ComputeAssertion(string actionExpression)
 #pragma warning restore RS0027 // API with optional parameter(s) should have the most parameters amongst its public overloads
     }
 
+    [StackTraceHidden]
     [InterpolatedStringHandler]
     [EditorBrowsable(EditorBrowsableState.Never)]
     public readonly struct AssertThrowsExactlyInterpolatedStringHandler<TException>

src/TestFramework/TestFramework/Assertions/Assert.cs

@@ -8,6 +8,7 @@ namespace Microsoft.VisualStudio.TestTools.UnitTesting;
 /// unit tests. If the condition being tested is not met, an exception
 /// is thrown.
 /// </summary>
+[StackTraceHidden]
 public sealed partial class Assert
 {
     private Assert()

src/TestFramework/TestFramework/Assertions/AssertScope.cs

@@ -9,6 +9,7 @@ namespace Microsoft.VisualStudio.TestTools.UnitTesting;
 /// Represents a scope in which assertion failures are collected instead of thrown immediately.
 /// When the scope is disposed, all collected failures are thrown as a single <see cref="AssertFailedException"/>.
 /// </summary>
+[StackTraceHidden]
 internal sealed class AssertScope : IDisposable
 {
     private static readonly AsyncLocal<AssertScope?> CurrentScope = new();

src/TestFramework/TestFramework/Assertions/AssertionValueRenderer.cs

@@ -6,6 +6,7 @@ namespace Microsoft.VisualStudio.TestTools.UnitTesting;
 /// <summary>
 /// Renders values for display in structured assertion messages following the RFC 012 value rendering rules.
 /// </summary>
+[StackTraceHidden]
 internal static class AssertionValueRenderer
 {
     /// <summary>

src/TestFramework/TestFramework/Assertions/CollectionAssert.cs

@@ -8,6 +8,7 @@ namespace Microsoft.VisualStudio.TestTools.UnitTesting;
 /// with collections within unit tests. If the condition being tested is not
 /// met, an exception is thrown.
 /// </summary>
+[StackTraceHidden]
 public sealed partial class CollectionAssert
 {
     #region Singleton constructor

src/TestFramework/TestFramework/Assertions/EvidenceBlock.cs

@@ -7,6 +7,7 @@ namespace Microsoft.VisualStudio.TestTools.UnitTesting;
 /// Represents the evidence block of a structured assertion message, containing labeled value lines
 /// such as expected/actual values and assertion-specific details.
 /// </summary>
+[StackTraceHidden]
 internal sealed class EvidenceBlock
 {
     private readonly List<EvidenceLine> _lines = [];

src/TestFramework/TestFramework/Assertions/EvidenceLine.cs

@@ -6,4 +6,5 @@ namespace Microsoft.VisualStudio.TestTools.UnitTesting;
 /// <summary>
 /// Represents a single labeled line in the evidence block of a structured assertion message.
 /// </summary>
+[StackTraceHidden]
 internal readonly record struct EvidenceLine(string Label, string Value);

src/TestFramework/TestFramework/Assertions/StringAssert.cs

@@ -6,6 +6,7 @@ namespace Microsoft.VisualStudio.TestTools.UnitTesting;
 /// <summary>
 /// The string assert.
 /// </summary>
+[StackTraceHidden]
 public sealed class StringAssert
 {
     #region Singleton constructor

src/TestFramework/TestFramework/Assertions/StructuredAssertionMessage.cs

@@ -14,6 +14,7 @@ namespace Microsoft.VisualStudio.TestTools.UnitTesting;
 /// <call-site expression>
 /// </code>
 /// </summary>
+[StackTraceHidden]
 internal sealed class StructuredAssertionMessage
 {
     private const string AssertionPrefix = "Assertion failed.";

test/IntegrationTests/MSTest.Acceptance.IntegrationTests/SoftAssertionTests.cs

@@ -41,7 +41,7 @@ public async Task ScopeWithMultipleFailures_TestFailsWithAggregatedMessage()
         // Validate the output includes the aggregate message and that inner exception stack traces
         // point to the test method (assertion call site).
         testHostResult.AssertOutputMatchesRegex(
-            """failed ScopeWithMultipleFailures \(\d+ms\)[\s\S]+2 assertion\(s\) failed within the assert scope\.[\s\S]+at Microsoft\.VisualStudio\.TestTools\.UnitTesting\.AssertScope\.Dispose\(\)[\s\S]+at UnitTest1\.ScopeWithMultipleFailures\(\)""");
+            """failed ScopeWithMultipleFailures \(\d+ms\)[\s\S]+2 assertion\(s\) failed within the assert scope\.[\s\S]+at UnitTest1\.ScopeWithMultipleFailures\(\)""");
     }
 
     [TestMethod]

test/UnitTests/Microsoft.Testing.Extensions.UnitTests/AzureDevOpsTests.cs

@@ -198,6 +198,81 @@ public void DoesNotSkipUserFrameWhoseTypeNameStartsWithAssert()
             $"\nLogs:\n{string.Join("\n", logger.Logs)}");
     }
 
+    [TestMethod]
+    public void RealAssertFailure_AnnotationPointsAtTestMethodAndNotAtFrameworkFile()
+    {
+        // End-to-end acceptance for https://github.com/microsoft/testfx/issues/8277.
+        //
+        // Trigger a *real* MSTest assertion failure (no synthetic stack trace) and ensure the
+        // AzDO reporter annotates the test method's source file rather than the framework
+        // partial-class file that actually holds the failing implementation.
+        //
+        // This regression is double-guarded:
+        //   * On .NET 6+: every public Assert/CollectionAssert/StringAssert method carries
+        //     [StackTraceHidden], so the framework frame should not even appear in the
+        //     captured stack trace.
+        //   * On older runtimes (.NET Framework / netstandard2.0 consumers): the attribute is
+        //     a no-op, but the reporter's type-prefix heuristic still skips the framework
+        //     frame.
+        // Either way, the annotation must point at this test method's source file.
+        (string testFile, _) = GetCurrentLocation();
+
+        AssertFailedException error;
+        try
+        {
+#pragma warning disable MSTEST0025 // Use 'Assert.Fail' instead of an always-failing assert - we deliberately want a real Assert.AreEqual failure so the captured stack trace reflects what users see.
+            Assert.AreEqual(1, 2);
+#pragma warning restore MSTEST0025
+            throw new InvalidOperationException("Expected AssertFailedException was not thrown.");
+        }
+        catch (AssertFailedException ex)
+        {
+            error = ex;
+        }
+
+        var logger = new TextLogger();
+        // Trim ##. If we keep it, then when the test fails, the assertion failure will get printed to screen and picked up incorrectly by AzDO, because it scans all output for the ##vso... pattern.
+        string? text = AzureDevOpsReporter.GetErrorText(
+            "MyTestDisplayName",
+            explanation: null,
+            error,
+            "severity",
+            new SystemFileSystem(),
+            logger,
+            "net9.0")?.TrimStart('#');
+
+        // Also neutralize any '##vso[' that the trace logger captured (the reporter logs the full
+        // command line at trace level) so the assertion failure messages below cannot smuggle a
+        // real AzDO command into the build output when this test fails on CI.
+        string safeLogs = string.Join("\n", logger.Logs).Replace("##vso[", "vso[");
+
+        Assert.IsNotNull(text, $"AzDO reporter should have produced an annotation. Logs:\n{safeLogs}");
+
+        // Mirror the path normalization performed by AzureDevOpsReporter.GetErrorText:
+        //  * Strip the deterministic-build root '/_/' (set by <ContinuousIntegrationBuild>true</ContinuousIntegrationBuild>
+        //    in CI), then fall back to stripping the runtime repo root for local builds.
+        //  * Normalize separators to '/'.
+        // Without this, the test breaks in CI where [CallerFilePath] returns '/_/test/...'
+        // but the reporter strips '/_/' and emits 'sourcepath=test/...'.
+        const string DeterministicBuildRoot = "/_/";
+        string normalizedTestFile = testFile.Replace('\\', '/');
+        string repoRoot = RootFinder.Find().Replace('\\', '/');
+        string expectedRelativeFile = normalizedTestFile.StartsWith(DeterministicBuildRoot, StringComparison.OrdinalIgnoreCase)
+            ? normalizedTestFile.Substring(DeterministicBuildRoot.Length)
+            : normalizedTestFile.StartsWith(repoRoot, StringComparison.OrdinalIgnoreCase)
+                ? normalizedTestFile.Substring(repoRoot.Length).TrimStart('/')
+                : normalizedTestFile;
+
+        Assert.Contains(
+            $"sourcepath={expectedRelativeFile};",
+            text,
+            $"AzDO annotation must point at the test method's source file. Got: {text}\nLogs:\n{safeLogs}");
+        Assert.DoesNotContain(
+            "/src/TestFramework/TestFramework/Assertions/",
+            text,
+            $"AzDO annotation must not point at a framework Assert partial-class file. Got: {text}\nLogs:\n{safeLogs}");
+    }
+
     [TestMethod]
     public void FormatErrorMessage_PlacesTestNameAsTitleOnFirstLine()
     {