Ensure matching nodes for valueOf assertion to be always present

Author: tompng

test/test_jaxen.rb

@@ -103,6 +103,8 @@ def process_nominal_test(context, variables, namespaces, test)
         assert_equal(Integer(expected, 10),
                      matched.size,
                      user_message(context, xpath, matched))
+      else
+        assert_operator(matched.size, :>, 0, user_message(context, xpath, matched))
       end
 
       XPath.each(test, "valueOf") do |value_of|