GetMergedNestedText is affected by #38 as well

Author: bodewig

RELEASE_NOTES.md

@@ -6,9 +6,11 @@
   be compared.
   Inspired by Issue [#xmlunit/259](https://github.com/xmlunit/xmlunit/issues/259)
 
-* `Nodes.StripElementContentWhitespace` had the same problem of not
-  knowning about `XmlWhitespace` that caused
-  Issue [#38](https://github.com/xmlunit/xmlunit.net/issues/38)
+* `Nodes.GetMergedNestedText` and
+  `Nodes.StripElementContentWhitespace` had the same problem of not
+  knowning about `XmlWhitespace` that caused Issue
+  [#38](https://github.com/xmlunit/xmlunit.net/issues/38). And neither
+  of the methods could deal with `XmlSignificantWhitespace` at all.
 
 ## XMLUnit.NET 2.9.2 - /Released 2023-03-16/
 

src/main/net-core/Util/Nodes.cs

@@ -40,7 +40,7 @@ public static XmlQualifiedName GetQName(this XmlNode n) {
         public static string GetMergedNestedText(XmlNode n) {
             return n.ChildNodes
                 .Cast<XmlNode>()
-                .Where(child => child is XmlText || child is XmlCDataSection)
+                .Where(child => IsTextualContentNode(child))
                 .Select(child => child.Value)
                 .Where(s => s != null)
                 .Aggregate(new StringBuilder(), (sb, s) => sb.Append(s))
@@ -147,7 +147,7 @@ private static void HandleWsRec(XmlNode n, bool normalize) {
             foreach (XmlNode child in n.ChildNodes) {
                 HandleWsRec(child, normalize);
                 if (!(n is XmlAttribute)
-                    && (child is XmlText || child is XmlCDataSection || child is XmlWhitespace)
+                    && IsTextualContentNode(child)
                     && child.Value.Length == 0) {
                     toRemove.AddLast(child);
                 }
@@ -199,7 +199,7 @@ private static void StripECW(XmlNode n) {
             foreach (XmlNode child in n.ChildNodes) {
                 StripECW(child);
                 if (!(n is XmlAttribute)
-                    && (child is XmlText || child is XmlCDataSection || child is XmlWhitespace)
+                    && IsTextualContentNode(child)
                     && child.Value.Trim().Length == 0) {
                     toRemove.AddLast(child);
                 }
@@ -208,5 +208,10 @@ private static void StripECW(XmlNode n) {
                 n.RemoveChild(child);
             }
         }
+
+        private static bool IsTextualContentNode(XmlNode n) {
+            return n is XmlText || n is XmlCDataSection || n is XmlWhitespace
+                || n is XmlSignificantWhitespace;
+        }
     }
 }