[System.XML] Add unit test for #18118

mcs/class/System.XML/System.Xml_test.dll.sources

@@ -112,3 +112,4 @@ System.Xml.Xsl/XsltCompileExceptionTests.cs
 System.Xml.Xsl/XsltExceptionCas.cs
 System.Xml.Xsl/XsltExceptionTests.cs
 System.Xml.XPath/XPathExceptionCas.cs
+System.Xml.Xsl/XslCompiledTransformTests.cs

mcs/class/System.XML/Test/System.Xml.Xsl/XslCompiledTransformTests.cs

@@ -0,0 +1,38 @@
+using NUnit.Framework;
+using System.IO;
+using System.Xml;
+using System.Xml.XPath;
+using System.Xml.Xsl;
+
+namespace MonoTests.System.Xml.Xsl
+{
+	[TestFixture]
+	public class XslCompiledTransformTests
+	{
+		[Test]
+		public void GlobalVariableReferencesAnotherGlobalVariable ()
+		{
+			string xsl = @"<xsl:stylesheet version='1.0'
+xmlns:xsl='http://www.w3.org/1999/XSL/Transform'>
+<xsl:variable name='global2'><xsl:value-of select='root/@attr' /></xsl:variable>
+<xsl:variable name='global1'>
+	<xsl:for-each select='//foo'>
+		<xsl:if test='@attr = $global2'>
+			<xsl:value-of select='name(.)' />: <xsl:value-of select='@attr' />
+		</xsl:if>
+	</xsl:for-each>
+</xsl:variable>
+<xsl:template match='/'>
+	<root>
+		<xsl:value-of select='$global1' />
+	</root>
+</xsl:template>
+</xsl:stylesheet>";
+			StringWriter sw = new StringWriter ();
+			XslCompiledTransform t = new XslCompiledTransform ();
+			t.Load (new XPathDocument (new StringReader (xsl)));
+			t.Transform (new XPathDocument (new XmlTextReader (new StringReader ("<root attr='B'><foo attr='A'/><foo attr='B'/><foo attr='C'/></root>"))), null, sw);
+			Assert.AreEqual ("<?xml version=\"1.0\" encoding=\"utf-16\"?><root>foo: B</root>", sw.ToString ());
+		}
+	}
+}