diff --git a/Rakefile b/Rakefile
index de1db20e..f93b8fef 100644
--- a/Rakefile
+++ b/Rakefile
@@ -19,9 +19,11 @@ end
 require 'rake/testtask'
 
 Rake::TestTask.new(:test) do |t|
+  t.libs << "test/lib"
+  t.ruby_opts << "-rhelper"
   t.test_files = FileList["test/**/test_*.rb"]
   if RUBY_VERSION >= "2.6"
-    t.ruby_opts = %w[--enable-frozen-string-literal --debug=frozen-string-literal]
+    t.ruby_opts << %w[--enable-frozen-string-literal --debug=frozen-string-literal]
   end
 end
 gem 'rake-compiler', '>= 0.4.1'
diff --git a/test/assets/mof.y b/test/assets/mof.y
index da317298..b241f74f 100644
--- a/test/assets/mof.y
+++ b/test/assets/mof.y
@@ -565,7 +565,7 @@ require 'rubygems'
 require 'cim'
 require File.join(File.dirname(__FILE__), 'result')
 require File.join(File.dirname(__FILE__), 'scanner')
-require File.join(File.dirname(__FILE__), 'helper')
+require File.join(File.dirname(__FILE__), 'case')
 
 ---- inner ----
 
diff --git a/test/helper.rb b/test/case.rb
similarity index 96%
rename from test/helper.rb
rename to test/case.rb
index 146beb5a..d5f9dad2 100644
--- a/test/helper.rb
+++ b/test/case.rb
@@ -3,11 +3,6 @@
 begin
 
 require 'test/unit'
-begin
-  require_relative './lib/core_assertions'
-  Test::Unit::TestCase.include Test::Unit::CoreAssertions
-rescue LoadError
-end
 require 'racc/static'
 require 'fileutils'
 require 'tempfile'
diff --git a/test/lib/helper.rb b/test/lib/helper.rb
new file mode 100644
index 00000000..d09927fd
--- /dev/null
+++ b/test/lib/helper.rb
@@ -0,0 +1,4 @@
+require_relative '../case'
+require_relative 'core_assertions'
+
+Racc::TestCase.include Test::Unit::CoreAssertions
diff --git a/test/regress/mof b/test/regress/mof
index 83660474..614bcc0c 100644
--- a/test/regress/mof
+++ b/test/regress/mof
@@ -14,7 +14,7 @@ require 'rubygems'
 require 'cim'
 require File.join(File.dirname(__FILE__), 'result')
 require File.join(File.dirname(__FILE__), 'scanner')
-require File.join(File.dirname(__FILE__), 'helper')
+require File.join(File.dirname(__FILE__), 'case')
 
 module MOF
   class Parser < Racc::Parser
diff --git a/test/test_chk_y.rb b/test/test_chk_y.rb
index bb8b6b4f..dfe5b093 100644
--- a/test/test_chk_y.rb
+++ b/test/test_chk_y.rb
@@ -1,4 +1,4 @@
-require File.expand_path(File.join(File.dirname(__FILE__), 'helper'))
+require File.expand_path(File.join(File.dirname(__FILE__), 'case'))
 
 module Racc
   class TestChkY < TestCase
diff --git a/test/test_grammar_file_parser.rb b/test/test_grammar_file_parser.rb
index b187bdca..ddfc0179 100644
--- a/test/test_grammar_file_parser.rb
+++ b/test/test_grammar_file_parser.rb
@@ -1,4 +1,4 @@
-require File.expand_path(File.join(File.dirname(__FILE__), 'helper'))
+require File.expand_path(File.join(File.dirname(__FILE__), 'case'))
 
 module Racc
   class TestGrammarFileParser < TestCase
diff --git a/test/test_racc_command.rb b/test/test_racc_command.rb
index 0d2c5829..77c57a32 100644
--- a/test/test_racc_command.rb
+++ b/test/test_racc_command.rb
@@ -1,4 +1,4 @@
-require File.expand_path(File.join(File.dirname(__FILE__), 'helper'))
+require File.expand_path(File.join(File.dirname(__FILE__), 'case'))
 
 module Racc
   class TestRaccCommand < TestCase
diff --git a/test/test_scan_y.rb b/test/test_scan_y.rb
index 4c601191..983e2f58 100644
--- a/test/test_scan_y.rb
+++ b/test/test_scan_y.rb
@@ -1,4 +1,4 @@
-require File.expand_path(File.join(File.dirname(__FILE__), 'helper'))
+require File.expand_path(File.join(File.dirname(__FILE__), 'case'))
 
 module Racc
   class TestScanY < TestCase