diff --git a/activesupport/test/core_ext/object/json_gem_encoding_test.rb b/activesupport/test/core_ext/object/json_gem_encoding_test.rb
index 4cdb6ed09f2d81f00d63c0e920c0d3094045c533..eef02f7458c1115af319f0bd12dc1308c91bbe36 100644
--- a/activesupport/test/core_ext/object/json_gem_encoding_test.rb
+++ b/activesupport/test/core_ext/object/json_gem_encoding_test.rb
@@ -22,7 +22,7 @@ class JsonGemEncodingTest < ActiveSupport::TestCase
 
   JSONTest::EncodingTestCases.constants.each_with_index do |name|
     JSONTest::EncodingTestCases.const_get(name).each_with_index do |(subject, _), i|
-      test("#{name[0..-6].underscore} #{i}") do
+      test("#{name[0..-6]} #{i}") do
         assert_same_with_or_without_active_support(subject)
       end
     end