test(jruby): capture incorrect ns behavior in a pending test

See #2543

ext/java/nokogiri/XmlNode.java

@@ -1207,6 +1207,18 @@ public class XmlNode extends RubyObject
 
     List<XmlNamespace> namespaces = doc.getNamespaceCache().get(node);
     return RubyArray.newArray(context.runtime, namespaces);
+
+    // // TODO: I think this implementation would be better but there are edge cases
+    // // See https://github.com/sparklemotion/nokogiri/issues/2543
+    // RubyArray<?> nsdefs = RubyArray.newArray(context.getRuntime());
+    // NamedNodeMap attrs = node.getAttributes();
+    // for (int j = 0 ; j < attrs.getLength() ; j++) {
+    //   Attr attr = (Attr)attrs.item(j);
+    //   if ("http://www.w3.org/2000/xmlns/" == attr.getNamespaceURI()) {
+    //     nsdefs.append(XmlNamespace.createFromAttr(context.getRuntime(), attr));
+    //   }
+    // }
+    // return nsdefs;
   }
 
   /**

test/namespaces/test_namespace_definitions.rb

@@ -13,4 +13,25 @@
     assert_equal("<a xmlns:foo=\"fooey\"/>", child1.to_xml)
     assert_equal("<b xmlns:foo=\"fooey\"/>", child2.to_xml)
   end
+
+  it "handles multiple instances of a namespace definition" do
+    # this describes behavior that is broken in JRuby related to the namespace cache and should be fixed
+    # see https://github.com/sparklemotion/nokogiri/issues/2543
+    doc = Nokogiri::XML::Document.parse("<root>")
+    child1 = doc.create_element("a", "xmlns:foo" => "http://nokogiri.org/ns/foo")
+    assert_equal(1, child1.namespace_definitions.length)
+    child1.namespace_definitions.first.tap do |ns|
+      assert_equal("foo", ns.prefix)
+      assert_equal("http://nokogiri.org/ns/foo", ns.href)
+    end
+
+    child2 = doc.create_element("b", "xmlns:foo" => "http://nokogiri.org/ns/foo")
+    pending_if("https://github.com/sparklemotion/nokogiri/issues/2543", Nokogiri.jruby?) do
+      assert_equal(1, child2.namespace_definitions.length)
+      child2.namespace_definitions.first.tap do |ns|
+        assert_equal("foo", ns.prefix)
+        assert_equal("http://nokogiri.org/ns/foo", ns.href)
+      end
+    end
+  end
 end