Fix staircase in logger (#4756)

Author: nohwnd

src/Microsoft.TestPlatform.Extensions.HtmlLogger/HtmlTransformer.cs

@@ -20,7 +20,7 @@ internal class HtmlTransformer : IHtmlTransformer
     public HtmlTransformer()
     {
         _xslTransform = new XslCompiledTransform();
-        _xslTransform.Load(XmlReader.Create(GetType().Assembly.GetManifestResourceStream("Microsoft.VisualStudio.TestPlatform.Extensions.HtmlLogger.Html.xslt") ?? throw new InvalidOperationException()));
+        _xslTransform.Load(XmlReader.Create(GetType().Assembly.GetManifestResourceStream("Microsoft.VisualStudio.TestPlatform.Extensions.HtmlLogger.Html.xslt") ?? throw new InvalidOperationException(), new XmlReaderSettings { CheckCharacters = false }));
     }
 
     /// <summary>
@@ -33,7 +33,9 @@ public void Transform(string xmlFile, string htmlFile)
         // for example &#xFFFF;. DCS will load them, but for XSL to load them here we need to pass it
         // a reader that we've configured to be tolerant of such references.
         using XmlReader xr = XmlReader.Create(xmlFile, new XmlReaderSettings() { CheckCharacters = false });
-        using XmlWriter xw = XmlWriter.Create(htmlFile, new XmlWriterSettings() { CheckCharacters = false });
+
+        // Use output settings from the xslt, especially the output method, which is HTML, which avoids outputting broken <div /> tags.
+        using XmlWriter xw = XmlWriter.Create(htmlFile, _xslTransform.OutputSettings);
 
         _xslTransform.Transform(xr, xw);
     }

test/Microsoft.TestPlatform.Acceptance.IntegrationTests/LoggerTests.cs

@@ -69,12 +69,21 @@ public void HtmlLoggerWithFriendlyNameContainsExpectedContent(RunnerInfo runnerI
         InvokeVsTest(arguments);
 
         var htmlLogFilePath = Path.Combine(TempDirectory.Path, htmlFileName);
-        XmlDocument report = new();
-        report.Load(htmlLogFilePath);
+        XmlDocument report = LoadReport(htmlLogFilePath);
 
         AssertExpectedHtml(report.DocumentElement!);
     }
 
+    private static XmlDocument LoadReport(string htmlLogFilePath)
+    {
+        // XML reader cannot handle <br> tags because they are not closed, and hence are not valid XML.
+        // They are correct HTML though, so we patch it here. 
+        var text = File.ReadAllText(htmlLogFilePath).Replace("<br>", "<br/>");
+        var report = new XmlDocument();
+        report.Load(new StringReader(text));
+        return report;
+    }
+
     [TestMethod]
     [NetCoreTargetFrameworkDataSource]
     public void TrxLoggerWithExecutorUriShouldProperlyOverwriteFile(RunnerInfo runnerInfo)