From da4646cd2dae5ce6cd62285e1d820c641decadd7 Mon Sep 17 00:00:00 2001
From: Jakub Jares <jajares@microsoft.com>
Date: Tue, 25 Aug 2026 15:01:27 +0200
Subject: [PATCH] Test that the HTML post-processor refuses to merge through a
 symlink

HtmlArtifactPostProcessor is the only one of the four artifact post-processors
whose reparse-point refusal has no test, so removing the guard at the call site
makes nothing in the repository fail. Add the symlink case and the dangling
symlink case to HtmlArtifactPostProcessorTests, matching the tests the Trx,
JUnit and Ctrf files already have.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
---
 .../HtmlArtifactPostProcessorTests.cs         | 86 +++++++++++++++++++
 1 file changed, 86 insertions(+)

diff --git a/test/UnitTests/Microsoft.Testing.Extensions.UnitTests/HtmlArtifactPostProcessorTests.cs b/test/UnitTests/Microsoft.Testing.Extensions.UnitTests/HtmlArtifactPostProcessorTests.cs
index d11adacbf0..40cd85492f 100644
--- a/test/UnitTests/Microsoft.Testing.Extensions.UnitTests/HtmlArtifactPostProcessorTests.cs
+++ b/test/UnitTests/Microsoft.Testing.Extensions.UnitTests/HtmlArtifactPostProcessorTests.cs
@@ -427,6 +427,92 @@ await Assert.ThrowsExactlyAsync<ArgumentException>(
         }
     }
 
+#if NETCOREAPP
+    [TestMethod]
+    public async Task ProcessAsync_WhenMergedDirectoryIsAReparsePoint_DoesNotMerge()
+    {
+        // 'merged' is a fixed, predictable child name under the orchestrator-supplied output directory.
+        // A symlink or junction planted at that name becomes the base the merge writes into, redirecting
+        // the merged report to wherever the link points and letting the run write outside the directory it
+        // was given, so the processor must refuse rather than write through it.
+        string root = CreateTemporaryDirectory();
+        string resultsDirectory = Path.Combine(root, "results");
+        string outsideDirectory = Path.Combine(root, "outside");
+        Directory.CreateDirectory(resultsDirectory);
+        Directory.CreateDirectory(outsideDirectory);
+        try
+        {
+            try
+            {
+                Directory.CreateSymbolicLink(Path.Combine(resultsDirectory, "merged"), outsideDirectory);
+            }
+            catch (Exception ex) when (ex is IOException or UnauthorizedAccessException or PlatformNotSupportedException)
+            {
+                // Creating a directory symlink needs elevation or Developer Mode on Windows.
+                Assert.Inconclusive("Host cannot create directory symbolic links.");
+                return;
+            }
+
+            string firstPath = Path.Combine(resultsDirectory, "first.html");
+            string secondPath = Path.Combine(resultsDirectory, "second.html");
+            File.WriteAllText(firstPath, CreateReport("first.dll", "MSTest", Epoch, Epoch, Test("a", "A", "passed", 1)));
+            File.WriteAllText(secondPath, CreateReport("second.dll", "MSTest", Epoch, Epoch, Test("b", "B", "passed", 2)));
+
+            ProcessedArtifact? output = await new HtmlArtifactPostProcessor().ProcessAsync(
+                [CreateInput(firstPath), CreateInput(secondPath)],
+                resultsDirectory,
+                new ArtifactPostProcessingContext(ArtifactPostProcessingTruncationReason.None),
+                CancellationToken.None);
+
+            Assert.IsNull(output);
+            Assert.IsEmpty(Directory.GetFileSystemEntries(outsideDirectory));
+        }
+        finally
+        {
+            Directory.Delete(root, recursive: true);
+        }
+    }
+
+    [TestMethod]
+    public async Task ProcessAsync_WhenMergedDirectoryIsADanglingReparsePoint_DoesNotMerge()
+    {
+        string root = CreateTemporaryDirectory();
+        string resultsDirectory = Path.Combine(root, "results");
+        string missingDirectory = Path.Combine(root, "missing");
+        Directory.CreateDirectory(resultsDirectory);
+        try
+        {
+            try
+            {
+                Directory.CreateSymbolicLink(Path.Combine(resultsDirectory, "merged"), missingDirectory);
+            }
+            catch (Exception ex) when (ex is IOException or UnauthorizedAccessException or PlatformNotSupportedException)
+            {
+                Assert.Inconclusive("Host cannot create directory symbolic links.");
+                return;
+            }
+
+            string firstPath = Path.Combine(resultsDirectory, "first.html");
+            string secondPath = Path.Combine(resultsDirectory, "second.html");
+            File.WriteAllText(firstPath, CreateReport("first.dll", "MSTest", Epoch, Epoch, Test("a", "A", "passed", 1)));
+            File.WriteAllText(secondPath, CreateReport("second.dll", "MSTest", Epoch, Epoch, Test("b", "B", "passed", 2)));
+
+            ProcessedArtifact? output = await new HtmlArtifactPostProcessor().ProcessAsync(
+                [CreateInput(firstPath), CreateInput(secondPath)],
+                resultsDirectory,
+                new ArtifactPostProcessingContext(ArtifactPostProcessingTruncationReason.None),
+                CancellationToken.None);
+
+            Assert.IsNull(output);
+            Assert.IsFalse(Directory.Exists(missingDirectory));
+        }
+        finally
+        {
+            Directory.Delete(root, recursive: true);
+        }
+    }
+#endif
+
     [TestMethod]
     public void CreateMergeId_IncludesExecutionProvenance()
     {