Use test-unit gem instead of test-suite of ruby core

.github/workflows/ci.yml

@@ -27,7 +27,6 @@ jobs:
         - 2.7
         - 2.6
         - 2.5
-        - 2.4
         - debug
         include:
         - { os: windows-latest , ruby: mingw }

Gemfile

@@ -1,4 +1,11 @@
 source 'https://rubygems.org'
 
-# Specify your gem's dependencies in bigdecimal.gemspec
 gemspec
+
+gem "benchmark_driver"
+gem "fiddle"
+gem "rake", ">= 12.3.3"
+gem "rake-compiler", ">= 0.9"
+gem "minitest", "< 5.0.0"
+gem "irb"
+gem "test-unit"

Rakefile

@@ -10,6 +10,7 @@ Rake::ExtensionTask.new('bigdecimal', spec)
 
 Rake::TestTask.new do |t|
   t.libs << 'test/lib'
+  t.ruby_opts << '-rhelper'
   t.test_files = FileList['test/bigdecimal/**/test_*.rb']
   t.warning = true
 end
@@ -41,3 +42,10 @@ end
 
 desc "Run all benchmarks"
 task benchmark: benchmark_tasks
+
+task :sync_tool do
+  require 'fileutils'
+  FileUtils.cp "../ruby/tool/lib/test/unit/core_assertions.rb", "./test/lib"
+  FileUtils.cp "../ruby/tool/lib/envutil.rb", "./test/lib"
+  FileUtils.cp "../ruby/tool/lib/find_executable.rb", "./test/lib"
+end

bigdecimal.gemspec

@@ -36,12 +36,5 @@ Gem::Specification.new do |s|
     sample/pi.rb
   ]
 
-  s.required_ruby_version = Gem::Requirement.new(">= 2.4.0")
-
-  s.add_development_dependency "benchmark_driver"
-  s.add_development_dependency "fiddle"
-  s.add_development_dependency "rake", ">= 12.3.3"
-  s.add_development_dependency "rake-compiler", ">= 0.9"
-  s.add_development_dependency "minitest", "< 5.0.0"
-  s.add_development_dependency "irb"
+  s.required_ruby_version = Gem::Requirement.new(">= 2.5.0")
 end

test/bigdecimal/test_ractor.rb

@@ -6,7 +6,7 @@ class TestBigDecimalRactor < Test::Unit::TestCase
 
   def setup
     super
-    skip unless defined? Ractor
+    omit_unless(defined? Ractor)
   end
 
   def test_ractor_shareable