Fix Xml.Linq test failures on ILC (#19860)

* Fix Xml.Linq.XNodeBuilder.Tests failures on ILC

* Fix Xml.Linq tests that need metadata

Author: sepidehkh

src/System.Private.Xml.Linq/tests/events/Resources/System.Xml.Linq.Events.Tests.rd.xml

@@ -0,0 +1,6 @@
+<Directives xmlns="http://schemas.microsoft.com/netfx/2013/01/metadata">
+  <Library>
+    <!-- Needed because of XCData instance in [Theory] data which causes xunit to reflect on its ToString() -->
+    <Type Name="System.Xml.Linq.XCData" Dynamic="Required Public" />
+  </Library>
+</Directives>

src/System.Private.Xml.Linq/tests/events/System.Xml.Linq.Events.Tests.csproj

@@ -21,5 +21,9 @@
     </ProjectReference>
     <ProjectReference Include="..\XDocument.Test.ModuleCore\XDocument.Test.ModuleCore.csproj" />
   </ItemGroup>
+
+  <ItemGroup>
+    <EmbeddedResource Include="Resources\$(AssemblyName).rd.xml" />
+  </ItemGroup>
   <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), dir.targets))\dir.targets" />
 </Project>

src/System.Private.Xml.Linq/tests/xNodeBuilder/CommonTests.cs

@@ -3413,12 +3413,14 @@ public void WriteCDataWithTwoClosingBrackets_5()
                         w.WriteEndElement();
                     }
 
-                    string expectedMsg = "Cannot have ']]>' inside an XML CDATA block.";
-
                     using (XmlReader reader = doc.CreateReader())
                     {
                         Exception exception = Assert.Throws<ArgumentException>(() => MoveToFirstElement(reader).ReadOuterXml());
-                        Assert.Equal(expectedMsg, exception.Message);
+                        if (!PlatformDetection.IsNetNative) // .Net Native toolchain optimizes away Exception messages
+                        {
+                            string expectedMsg = "Cannot have ']]>' inside an XML CDATA block.";
+                            Assert.Equal(expectedMsg, exception.Message);
+                        }
                     }
                 }
 
@@ -3605,12 +3607,14 @@ public void WriteCommentWithDoubleHyphensInValue()
                         w.WriteEndElement();
                     }
 
-                    string expectedMsg = "An XML comment cannot contain '--', and '-' cannot be the last character.";
-
                     using (XmlReader reader = doc.CreateReader())
                     {
                         Exception exception = Assert.Throws<ArgumentException>(() => MoveToFirstElement(reader).ReadOuterXml());
-                        Assert.Equal(expectedMsg, exception.Message);
+                        if (!PlatformDetection.IsNetNative) // .Net Native toolchain optimizes away Exception messages
+                        {
+                            string expectedMsg = "An XML comment cannot contain '--', and '-' cannot be the last character.";
+                            Assert.Equal(expectedMsg, exception.Message);
+                        }
                     }
                 }
             }
@@ -4206,12 +4210,14 @@ public void IncludePIEndTagAsPartOfTextValue()
                         w.WriteEndElement();
                     }
 
-                    string expectedMsg = "Cannot have '?>' inside an XML processing instruction.";
-
                     using (XmlReader reader = doc.CreateReader())
                     {
                         Exception exception = Assert.Throws<ArgumentException>(() => MoveToFirstElement(reader).ReadOuterXml());
-                        Assert.Equal(expectedMsg, exception.Message);
+                        if (!PlatformDetection.IsNetNative) // .Net Native toolchain optimizes away Exception messages
+                        {
+                            string expectedMsg = "Cannot have '?>' inside an XML processing instruction.";
+                            Assert.Equal(expectedMsg, exception.Message);
+                        }
                     }
                 }
 

src/System.Private.Xml.Linq/tests/xNodeBuilder/System.Xml.Linq.xNodeBuilder.Tests.csproj

@@ -13,6 +13,9 @@
     <Compile Include="$(CommonTestPath)\System\Collections\DictionaryExtensions.cs">
       <Link>Common\System\Collections\DictionaryExtensions.cs</Link>
     </Compile>
+    <Compile Include="$(CommonTestPath)\System\PlatformDetection.cs">
+      <Link>Common\System\PlatformDetection.cs</Link>
+    </Compile>
     <Compile Include="CommonTests.cs" />
     <Compile Include="EndOfLineHandlingTests.cs" />
     <Compile Include="ErrorConditions.cs" />