test: repro namespace_scopes compaction issue

Co-Authored-By: Matt Valentine-House <matt@eightbitraptor.com>
Co-Authored-By: Peter Zhu <peter@peterzhu.ca>

test/test_compaction.rb

@@ -3,19 +3,41 @@
 require "helper"
 
 describe "compaction" do
-  it "https://github.com/sparklemotion/nokogiri/pull/2579" do
-    skip unless GC.respond_to?(:verify_compaction_references)
+  describe Nokogiri::XML::Node do
+    it "compacts safely" do # https://github.com/sparklemotion/nokogiri/pull/2579
+      skip unless GC.respond_to?(:verify_compaction_references)
 
-    big_doc = "<root>" + ("a".."zz").map { |x| "<#{x}>#{x}</#{x}>" }.join + "</root>"
-    doc = Nokogiri.XML(big_doc)
+      big_doc = "<root>" + ("a".."zz").map { |x| "<#{x}>#{x}</#{x}>" }.join + "</root>"
+      doc = Nokogiri.XML(big_doc)
 
-    # ensure a bunch of node objects have been wrapped
-    doc.root.children.each(&:inspect)
+      # ensure a bunch of node objects have been wrapped
+      doc.root.children.each(&:inspect)
 
-    # compact the heap and try to get the node wrappers to move
-    GC.verify_compaction_references(double_heap: true, toward: :empty)
+      # compact the heap and try to get the node wrappers to move
+      GC.verify_compaction_references(double_heap: true, toward: :empty)
 
-    # access the node wrappers and make sure they didn't move
-    doc.root.children.each(&:inspect)
+      # access the node wrappers and make sure they didn't move
+      doc.root.children.each(&:inspect)
+    end
+  end
+
+  describe Nokogiri::XML::Namespace do
+    it "namespace_scopes" do
+      skip unless GC.respond_to?(:verify_compaction_references)
+
+      doc = Nokogiri::XML(<<~EOF)
+        <root xmlns="http://example.com/root" xmlns:bar="http://example.com/bar">
+          <first/>
+          <second xmlns="http://example.com/child"/>
+          <third xmlns:foo="http://example.com/foo"/>
+        </root>
+      EOF
+
+      doc.at_xpath("//root:first", "root" => "http://example.com/root").namespace_scopes.inspect
+
+      GC.verify_compaction_references(double_heap: true, toward: :empty)
+
+      doc.at_xpath("//root:first", "root" => "http://example.com/root").namespace_scopes.inspect
+    end
   end
 end