Add skipped test for empty summary element behavior

Author: sharwell

StyleCop.Analyzers/StyleCop.Analyzers.Test/HelperTests/XmlSyntaxFactoryTests.cs

@@ -57,6 +57,17 @@ public void TestSummaryElement()
             Assert.Equal(expected, XmlSyntaxFactory.SummaryElement("\r\n", XmlSyntaxFactory.Text("Summary.")).ToFullString());
         }
 
+        [Fact(Skip = "https://github.com/DotNetAnalyzers/StyleCopAnalyzers/issues/2672")]
+        [WorkItem(2672, "https://github.com/DotNetAnalyzers/StyleCopAnalyzers/issues/2672")]
+        public void TestEmptySummaryElement()
+        {
+            string expected =
+                "<summary>\r\n"
+                + "///\r\n"
+                + "/// </summary>";
+            Assert.Equal(expected, XmlSyntaxFactory.SummaryElement("\r\n").ToFullString());
+        }
+
         [Fact]
         public void TestRemarksElement()
         {