Use test-unit-ruby-core gem

Author: hsbt

.github/workflows/test.yml

@@ -26,4 +26,4 @@ jobs:
     - name: Install dependencies
       run: bundle install
     - name: Run test
-      run: rake test
+      run: bundle exec rake test

Gemfile

@@ -5,3 +5,4 @@ gemspec
 gem "bundler"
 gem "rake"
 gem "test-unit"
+gem "test-unit-ruby-core"

Rakefile

@@ -7,11 +7,4 @@ Rake::TestTask.new(:test) do |t|
   t.test_files = FileList["test/**/test_*.rb"]
 end
 
-task :sync_tool do
-  require 'fileutils'
-  FileUtils.cp "../ruby/tool/lib/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
-
 task :default => :test