diff --git a/lib/rdoc/markup/formatter_test_case.rb b/lib/rdoc/markup/formatter_test_case.rb
index 076b7c81bb..d1e8923681 100644
--- a/lib/rdoc/markup/formatter_test_case.rb
+++ b/lib/rdoc/markup/formatter_test_case.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest/unit'
+require 'test-unit'
 
 ##
 # Test case for creating new RDoc::Markup formatters.  See
diff --git a/test/rdoc/minitest_helper.rb b/test/rdoc/helper.rb
similarity index 94%
rename from test/rdoc/minitest_helper.rb
rename to test/rdoc/helper.rb
index 5db0c315ef..34849a2e2c 100644
--- a/test/rdoc/minitest_helper.rb
+++ b/test/rdoc/helper.rb
@@ -1,13 +1,13 @@
 # frozen_string_literal: true
 require 'bundler/errors'
 begin
-  gem 'minitest', '~> 5.0'
+  gem 'test-unit'
 rescue NoMethodError, Gem::LoadError, Bundler::GemfileNotFound
   # for ruby tests
 end
 
-require 'minitest/autorun'
-require 'minitest/benchmark' unless ENV['NOBENCHMARK']
+require 'test-unit'
+# require 'minitest/benchmark' unless ENV['NOBENCHMARK']
 
 require 'fileutils'
 require 'pp'
@@ -30,7 +30,7 @@
 # * <code>@pwd</code> containing the current working directory
 # * FileUtils, pp, Tempfile, Dir.tmpdir and StringIO
 
-class RDoc::TestCase < (defined?(Minitest::Test) ? Minitest::Test : MiniTest::Unit::TestCase)
+class RDoc::TestCase < Test::Unit::TestCase
 
   ##
   # Abstract test-case setup
@@ -192,7 +192,7 @@ def verb *parts
   # run capture_io with setting $VERBOSE = true
 
   def verbose_capture_io
-    capture_io do
+    capture_output do
       begin
         orig_verbose = $VERBOSE
         $VERBOSE = true
@@ -202,4 +202,7 @@ def verbose_capture_io
       end
     end
   end
+
+  alias capture_io capture_output
+  alias skip omit
 end
diff --git a/test/rdoc/test_rdoc_attr.rb b/test/rdoc/test_rdoc_attr.rb
index 5910c0fad3..cff52acf31 100644
--- a/test/rdoc/test_rdoc_attr.rb
+++ b/test/rdoc/test_rdoc_attr.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocAttr < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_comment.rb b/test/rdoc/test_rdoc_comment.rb
index 48d0042f16..add4f98398 100644
--- a/test/rdoc/test_rdoc_comment.rb
+++ b/test/rdoc/test_rdoc_comment.rb
@@ -1,7 +1,7 @@
 # coding: us-ascii
 # frozen_string_literal: true
 
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocComment < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_context_section.rb b/test/rdoc/test_rdoc_context_section.rb
index 93cfbdf0a7..ac1d9f9be8 100644
--- a/test/rdoc/test_rdoc_context_section.rb
+++ b/test/rdoc/test_rdoc_context_section.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocContextSection < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_encoding.rb b/test/rdoc/test_rdoc_encoding.rb
index 5b2de47aa2..41a8465395 100644
--- a/test/rdoc/test_rdoc_encoding.rb
+++ b/test/rdoc/test_rdoc_encoding.rb
@@ -1,7 +1,7 @@
 # coding: US-ASCII
 # frozen_string_literal: true
 
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocEncoding < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_generator_darkfish.rb b/test/rdoc/test_rdoc_generator_darkfish.rb
index edabe4fad4..f5858bce6e 100644
--- a/test/rdoc/test_rdoc_generator_darkfish.rb
+++ b/test/rdoc/test_rdoc_generator_darkfish.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocGeneratorDarkfish < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_generator_json_index.rb b/test/rdoc/test_rdoc_generator_json_index.rb
index 3281cac304..6a95acef73 100644
--- a/test/rdoc/test_rdoc_generator_json_index.rb
+++ b/test/rdoc/test_rdoc_generator_json_index.rb
@@ -1,7 +1,7 @@
 # coding: US-ASCII
 # frozen_string_literal: true
 
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocGeneratorJsonIndex < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_generator_markup.rb b/test/rdoc/test_rdoc_generator_markup.rb
index 5588d9c5f0..5491b7c61e 100644
--- a/test/rdoc/test_rdoc_generator_markup.rb
+++ b/test/rdoc/test_rdoc_generator_markup.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocGeneratorMarkup < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_generator_pot.rb b/test/rdoc/test_rdoc_generator_pot.rb
index 26641345ef..bafe9ecca5 100644
--- a/test/rdoc/test_rdoc_generator_pot.rb
+++ b/test/rdoc/test_rdoc_generator_pot.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocGeneratorPOT < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_generator_pot_po.rb b/test/rdoc/test_rdoc_generator_pot_po.rb
index c50899d446..7696a1f5b1 100644
--- a/test/rdoc/test_rdoc_generator_pot_po.rb
+++ b/test/rdoc/test_rdoc_generator_pot_po.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocGeneratorPOTPO < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_generator_pot_po_entry.rb b/test/rdoc/test_rdoc_generator_pot_po_entry.rb
index f3bf329348..d3d6271b23 100644
--- a/test/rdoc/test_rdoc_generator_pot_po_entry.rb
+++ b/test/rdoc/test_rdoc_generator_pot_po_entry.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocGeneratorPOTPOEntry < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_generator_ri.rb b/test/rdoc/test_rdoc_generator_ri.rb
index a33f5ca2ac..195c0d2482 100644
--- a/test/rdoc/test_rdoc_generator_ri.rb
+++ b/test/rdoc/test_rdoc_generator_ri.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocGeneratorRI < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_i18n_locale.rb b/test/rdoc/test_rdoc_i18n_locale.rb
index c936a7219f..43fd7e2197 100644
--- a/test/rdoc/test_rdoc_i18n_locale.rb
+++ b/test/rdoc/test_rdoc_i18n_locale.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocI18nLocale < RDoc::TestCase
 
@@ -23,9 +23,9 @@ def test_name
   end
 
   def test_load_nonexistent_po
-    File.stub(:exist?, false) do
-      refute @locale.load('nonexsitent-locale')
-    end
+    locale = File.join(@locale_dir, 'nonexsitent-locale')
+    refute_file locale
+    refute @locale.load(locale)
   end
 
   def test_load_existent_po
diff --git a/test/rdoc/test_rdoc_i18n_text.rb b/test/rdoc/test_rdoc_i18n_text.rb
index beb9f307a7..89b7e97708 100644
--- a/test/rdoc/test_rdoc_i18n_text.rb
+++ b/test/rdoc/test_rdoc_i18n_text.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocI18nText < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_markdown.rb b/test/rdoc/test_rdoc_markdown.rb
index 8b58150f8a..73e014288a 100644
--- a/test/rdoc/test_rdoc_markdown.rb
+++ b/test/rdoc/test_rdoc_markdown.rb
@@ -1,7 +1,7 @@
 # coding: UTF-8
 # frozen_string_literal: true
 
-require 'minitest_helper'
+require_relative 'helper'
 require 'rdoc/markup/block_quote'
 require 'rdoc/markdown'
 
diff --git a/test/rdoc/test_rdoc_markdown_test.rb b/test/rdoc/test_rdoc_markdown_test.rb
index 6445fb5e65..fff68818b5 100644
--- a/test/rdoc/test_rdoc_markdown_test.rb
+++ b/test/rdoc/test_rdoc_markdown_test.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 require 'pp'
 
 require 'rdoc'
diff --git a/test/rdoc/test_rdoc_markup.rb b/test/rdoc/test_rdoc_markup.rb
index 2812a2994f..b9bdafab2a 100644
--- a/test/rdoc/test_rdoc_markup.rb
+++ b/test/rdoc/test_rdoc_markup.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocMarkup < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_markup_attribute_manager.rb b/test/rdoc/test_rdoc_markup_attribute_manager.rb
index d6eccdf76f..ccc0664405 100644
--- a/test/rdoc/test_rdoc_markup_attribute_manager.rb
+++ b/test/rdoc/test_rdoc_markup_attribute_manager.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocMarkupAttributeManager < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_markup_attributes.rb b/test/rdoc/test_rdoc_markup_attributes.rb
index e592fa7145..0dfd72bdb6 100644
--- a/test/rdoc/test_rdoc_markup_attributes.rb
+++ b/test/rdoc/test_rdoc_markup_attributes.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocMarkupAttributes < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_markup_document.rb b/test/rdoc/test_rdoc_markup_document.rb
index 8202916238..7ada5374ec 100644
--- a/test/rdoc/test_rdoc_markup_document.rb
+++ b/test/rdoc/test_rdoc_markup_document.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocMarkupDocument < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_markup_formatter.rb b/test/rdoc/test_rdoc_markup_formatter.rb
index cdc5944cdf..8702db379d 100644
--- a/test/rdoc/test_rdoc_markup_formatter.rb
+++ b/test/rdoc/test_rdoc_markup_formatter.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocMarkupFormatter < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_markup_hard_break.rb b/test/rdoc/test_rdoc_markup_hard_break.rb
index 1d6c8927b5..adebfdc311 100644
--- a/test/rdoc/test_rdoc_markup_hard_break.rb
+++ b/test/rdoc/test_rdoc_markup_hard_break.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocMarkupHardBreak < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_markup_heading.rb b/test/rdoc/test_rdoc_markup_heading.rb
index 4508561a79..05a8e005ba 100644
--- a/test/rdoc/test_rdoc_markup_heading.rb
+++ b/test/rdoc/test_rdoc_markup_heading.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocMarkupHeading < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_markup_include.rb b/test/rdoc/test_rdoc_markup_include.rb
index 6b2d570286..9126526b73 100644
--- a/test/rdoc/test_rdoc_markup_include.rb
+++ b/test/rdoc/test_rdoc_markup_include.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocMarkupInclude < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_markup_indented_paragraph.rb b/test/rdoc/test_rdoc_markup_indented_paragraph.rb
index 06dcb25357..7b5758998f 100644
--- a/test/rdoc/test_rdoc_markup_indented_paragraph.rb
+++ b/test/rdoc/test_rdoc_markup_indented_paragraph.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocMarkupIndentedParagraph < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_markup_paragraph.rb b/test/rdoc/test_rdoc_markup_paragraph.rb
index 00e4320119..ca89a74fc3 100644
--- a/test/rdoc/test_rdoc_markup_paragraph.rb
+++ b/test/rdoc/test_rdoc_markup_paragraph.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocMarkupParagraph < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_markup_parser.rb b/test/rdoc/test_rdoc_markup_parser.rb
index 344d67df39..bea8cd9a34 100644
--- a/test/rdoc/test_rdoc_markup_parser.rb
+++ b/test/rdoc/test_rdoc_markup_parser.rb
@@ -1,7 +1,7 @@
 # coding: utf-8
 # frozen_string_literal: true
 
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocMarkupParser < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_markup_pre_process.rb b/test/rdoc/test_rdoc_markup_pre_process.rb
index 60ec75c19e..b4acd4ebe3 100644
--- a/test/rdoc/test_rdoc_markup_pre_process.rb
+++ b/test/rdoc/test_rdoc_markup_pre_process.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocMarkupPreProcess < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_markup_raw.rb b/test/rdoc/test_rdoc_markup_raw.rb
index 95de62208a..c7795b24e1 100644
--- a/test/rdoc/test_rdoc_markup_raw.rb
+++ b/test/rdoc/test_rdoc_markup_raw.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocMarkupRaw < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_markup_to_ansi.rb b/test/rdoc/test_rdoc_markup_to_ansi.rb
index 4c312e7972..1d1fc7db46 100644
--- a/test/rdoc/test_rdoc_markup_to_ansi.rb
+++ b/test/rdoc/test_rdoc_markup_to_ansi.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocMarkupToAnsi < RDoc::Markup::TextFormatterTestCase
 
diff --git a/test/rdoc/test_rdoc_markup_to_bs.rb b/test/rdoc/test_rdoc_markup_to_bs.rb
index f269790357..7ebde481e6 100644
--- a/test/rdoc/test_rdoc_markup_to_bs.rb
+++ b/test/rdoc/test_rdoc_markup_to_bs.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocMarkupToBs < RDoc::Markup::TextFormatterTestCase
 
diff --git a/test/rdoc/test_rdoc_markup_to_html.rb b/test/rdoc/test_rdoc_markup_to_html.rb
index c30c89a7e3..fb94269064 100644
--- a/test/rdoc/test_rdoc_markup_to_html.rb
+++ b/test/rdoc/test_rdoc_markup_to_html.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocMarkupToHtml < RDoc::Markup::FormatterTestCase
 
diff --git a/test/rdoc/test_rdoc_markup_to_html_snippet.rb b/test/rdoc/test_rdoc_markup_to_html_snippet.rb
index 7e01413dda..94f58b6529 100644
--- a/test/rdoc/test_rdoc_markup_to_html_snippet.rb
+++ b/test/rdoc/test_rdoc_markup_to_html_snippet.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocMarkupToHtmlSnippet < RDoc::Markup::FormatterTestCase
 
diff --git a/test/rdoc/test_rdoc_markup_to_joined_paragraph.rb b/test/rdoc/test_rdoc_markup_to_joined_paragraph.rb
index b4eed5f601..cbaf75a04e 100644
--- a/test/rdoc/test_rdoc_markup_to_joined_paragraph.rb
+++ b/test/rdoc/test_rdoc_markup_to_joined_paragraph.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocMarkupToJoinedParagraph < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_markup_to_label.rb b/test/rdoc/test_rdoc_markup_to_label.rb
index b869745528..70ea7f0f1b 100644
--- a/test/rdoc/test_rdoc_markup_to_label.rb
+++ b/test/rdoc/test_rdoc_markup_to_label.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocMarkupToLabel < RDoc::Markup::FormatterTestCase
 
diff --git a/test/rdoc/test_rdoc_markup_to_markdown.rb b/test/rdoc/test_rdoc_markup_to_markdown.rb
index 9c5b6d3e57..4d3a005381 100644
--- a/test/rdoc/test_rdoc_markup_to_markdown.rb
+++ b/test/rdoc/test_rdoc_markup_to_markdown.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocMarkupToMarkdown < RDoc::Markup::TextFormatterTestCase
 
diff --git a/test/rdoc/test_rdoc_markup_to_rdoc.rb b/test/rdoc/test_rdoc_markup_to_rdoc.rb
index e81bc2f1ad..1d833b156a 100644
--- a/test/rdoc/test_rdoc_markup_to_rdoc.rb
+++ b/test/rdoc/test_rdoc_markup_to_rdoc.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocMarkupToRDoc < RDoc::Markup::TextFormatterTestCase
 
diff --git a/test/rdoc/test_rdoc_markup_to_table_of_contents.rb b/test/rdoc/test_rdoc_markup_to_table_of_contents.rb
index bfeb2d6f58..11ab6f197b 100644
--- a/test/rdoc/test_rdoc_markup_to_table_of_contents.rb
+++ b/test/rdoc/test_rdoc_markup_to_table_of_contents.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocMarkupToTableOfContents < RDoc::Markup::FormatterTestCase
 
diff --git a/test/rdoc/test_rdoc_markup_to_tt_only.rb b/test/rdoc/test_rdoc_markup_to_tt_only.rb
index 856eb592c5..8508f823df 100644
--- a/test/rdoc/test_rdoc_markup_to_tt_only.rb
+++ b/test/rdoc/test_rdoc_markup_to_tt_only.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocMarkupToTtOnly < RDoc::Markup::FormatterTestCase
 
diff --git a/test/rdoc/test_rdoc_markup_verbatim.rb b/test/rdoc/test_rdoc_markup_verbatim.rb
index 88ca4906bb..1a650c44ef 100644
--- a/test/rdoc/test_rdoc_markup_verbatim.rb
+++ b/test/rdoc/test_rdoc_markup_verbatim.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocMarkupVerbatim < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_options.rb b/test/rdoc/test_rdoc_options.rb
index b6769d14b3..ade4d0bedb 100644
--- a/test/rdoc/test_rdoc_options.rb
+++ b/test/rdoc/test_rdoc_options.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocOptions < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_parser.rb b/test/rdoc/test_rdoc_parser.rb
index 2638adcd15..a2b5d957a7 100644
--- a/test/rdoc/test_rdoc_parser.rb
+++ b/test/rdoc/test_rdoc_parser.rb
@@ -1,7 +1,7 @@
 # -*- coding: us-ascii -*-
 # frozen_string_literal: true
 
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocParser < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_parser_c.rb b/test/rdoc/test_rdoc_parser_c.rb
index ca668f61fc..720c3730ab 100644
--- a/test/rdoc/test_rdoc_parser_c.rb
+++ b/test/rdoc/test_rdoc_parser_c.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 =begin
   TODO: test call-seq parsing
diff --git a/test/rdoc/test_rdoc_parser_changelog.rb b/test/rdoc/test_rdoc_parser_changelog.rb
index 18ea81b34e..cb6406259c 100644
--- a/test/rdoc/test_rdoc_parser_changelog.rb
+++ b/test/rdoc/test_rdoc_parser_changelog.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocParserChangeLog < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_parser_markdown.rb b/test/rdoc/test_rdoc_parser_markdown.rb
index 30e66e2833..06c6700d96 100644
--- a/test/rdoc/test_rdoc_parser_markdown.rb
+++ b/test/rdoc/test_rdoc_parser_markdown.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocParserMarkdown < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_parser_rd.rb b/test/rdoc/test_rdoc_parser_rd.rb
index 15112fdb0e..bac9c65592 100644
--- a/test/rdoc/test_rdoc_parser_rd.rb
+++ b/test/rdoc/test_rdoc_parser_rd.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocParserRd < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_parser_ruby.rb b/test/rdoc/test_rdoc_parser_ruby.rb
index 95a8658fdb..fde722a130 100644
--- a/test/rdoc/test_rdoc_parser_ruby.rb
+++ b/test/rdoc/test_rdoc_parser_ruby.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocParserRuby < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_parser_simple.rb b/test/rdoc/test_rdoc_parser_simple.rb
index 5bde34b746..2f1ad00de4 100644
--- a/test/rdoc/test_rdoc_parser_simple.rb
+++ b/test/rdoc/test_rdoc_parser_simple.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocParserSimple < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_rd.rb b/test/rdoc/test_rdoc_rd.rb
index 70bb94d24b..83ee423455 100644
--- a/test/rdoc/test_rdoc_rd.rb
+++ b/test/rdoc/test_rdoc_rd.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocRd < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_rd_block_parser.rb b/test/rdoc/test_rdoc_rd_block_parser.rb
index 0f0bc4f891..22f432eaf4 100644
--- a/test/rdoc/test_rdoc_rd_block_parser.rb
+++ b/test/rdoc/test_rdoc_rd_block_parser.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocRdBlockParser < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_rd_inline.rb b/test/rdoc/test_rdoc_rd_inline.rb
index dbba164865..13ab86d3d9 100644
--- a/test/rdoc/test_rdoc_rd_inline.rb
+++ b/test/rdoc/test_rdoc_rd_inline.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocRdInline < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_rd_inline_parser.rb b/test/rdoc/test_rdoc_rd_inline_parser.rb
index 3673de48e1..9aff6139bc 100644
--- a/test/rdoc/test_rdoc_rd_inline_parser.rb
+++ b/test/rdoc/test_rdoc_rd_inline_parser.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocRdInlineParser < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_rdoc.rb b/test/rdoc/test_rdoc_rdoc.rb
index 3bce54b243..f7eec1a5b8 100644
--- a/test/rdoc/test_rdoc_rdoc.rb
+++ b/test/rdoc/test_rdoc_rdoc.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocRDoc < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_ri_driver.rb b/test/rdoc/test_rdoc_ri_driver.rb
index 18dcb5b68a..16a3efcbf3 100644
--- a/test/rdoc/test_rdoc_ri_driver.rb
+++ b/test/rdoc/test_rdoc_ri_driver.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocRIDriver < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_ri_paths.rb b/test/rdoc/test_rdoc_ri_paths.rb
index eb9b7fc93c..01ade58dad 100644
--- a/test/rdoc/test_rdoc_ri_paths.rb
+++ b/test/rdoc/test_rdoc_ri_paths.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocRIPaths < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_servlet.rb b/test/rdoc/test_rdoc_servlet.rb
index b772eeaddf..b26ce28c3a 100644
--- a/test/rdoc/test_rdoc_servlet.rb
+++ b/test/rdoc/test_rdoc_servlet.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocServlet < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_single_class.rb b/test/rdoc/test_rdoc_single_class.rb
index e4123cb9bc..ee242d7bc9 100644
--- a/test/rdoc/test_rdoc_single_class.rb
+++ b/test/rdoc/test_rdoc_single_class.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocSingleClass < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_stats.rb b/test/rdoc/test_rdoc_stats.rb
index cac30d15aa..b9918e4fd3 100644
--- a/test/rdoc/test_rdoc_stats.rb
+++ b/test/rdoc/test_rdoc_stats.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocStats < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_task.rb b/test/rdoc/test_rdoc_task.rb
index 3ce8529aef..9bdc4e3f09 100644
--- a/test/rdoc/test_rdoc_task.rb
+++ b/test/rdoc/test_rdoc_task.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 begin
   require 'rake'
 rescue LoadError
diff --git a/test/rdoc/test_rdoc_text.rb b/test/rdoc/test_rdoc_text.rb
index fcd993f834..5e38c6144f 100644
--- a/test/rdoc/test_rdoc_text.rb
+++ b/test/rdoc/test_rdoc_text.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require 'minitest_helper'
+require_relative 'helper'
 require 'timeout'
 
 class TestRDocText < RDoc::TestCase
diff --git a/test/rdoc/test_rdoc_token_stream.rb b/test/rdoc/test_rdoc_token_stream.rb
index c946d0f1ef..cdfa615dae 100644
--- a/test/rdoc/test_rdoc_token_stream.rb
+++ b/test/rdoc/test_rdoc_token_stream.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocTokenStream < RDoc::TestCase
 
diff --git a/test/rdoc/test_rdoc_tom_doc.rb b/test/rdoc/test_rdoc_tom_doc.rb
index 27a3e6f178..ddecea4b21 100644
--- a/test/rdoc/test_rdoc_tom_doc.rb
+++ b/test/rdoc/test_rdoc_tom_doc.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'minitest_helper'
+require_relative 'helper'
 
 class TestRDocTomDoc < RDoc::TestCase
 
diff --git a/test/rdoc/xref_test_case.rb b/test/rdoc/xref_test_case.rb
index d42cf398e7..5e6612d382 100644
--- a/test/rdoc/xref_test_case.rb
+++ b/test/rdoc/xref_test_case.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 ENV['RDOC_TEST'] = 'yes'
 
-require 'minitest_helper'
+require_relative 'helper'
 require File.expand_path '../xref_data', __FILE__
 
 class XrefTestCase < RDoc::TestCase