新規gemを作るときは、bundle gemを使う。

bundle-gem - Generate a project skeleton for creating a rubygem

Generates a directory named GEM_NAME with a Rakefile, GEM_NAME.gemspec, and other supporting files and directories that can be used to develop a rubygem with that name.

via. Bundler: bundle gem

実行してみた

オプションなしで実行すると下記のように、ファイルが作成される。

$ bundle gem sample-gem-name
Creating gem 'sample-gem-name'...
MIT License enabled in config
Changelog enabled in config
Standard enabled in config
Initializing git repo in /Users/toshimaru/xxx/sample-gem-name
      create  sample-gem-name/Gemfile
      create  sample-gem-name/lib/sample/gem/name.rb
      create  sample-gem-name/lib/sample/gem/name/version.rb
      create  sample-gem-name/sig/sample/gem/name.rbs
      create  sample-gem-name/sample-gem-name.gemspec
      create  sample-gem-name/Rakefile
      create  sample-gem-name/README.md
      create  sample-gem-name/bin/console
      create  sample-gem-name/bin/setup
      create  sample-gem-name/.gitignore
      create  sample-gem-name/test/test_helper.rb
      create  sample-gem-name/test/sample/gem/name_test.rb
      create  sample-gem-name/.github/workflows/main.yml
      create  sample-gem-name/LICENSE.txt
      create  sample-gem-name/CHANGELOG.md
      create  sample-gem-name/.standard.yml
Gem 'sample-gem-name' was successfully created. For more information on making a RubyGem visit https://bundler.io/guides/creating_gem.html

test フレームワークを指定

--test=minitest でテストフレームワークを指定できる。

$ bundle gem xxx --test=minitest