Rails test无法运行：找不到arel/visitors/mysql文件报错求助

问题情况 #

刚接触Rails框架，项目其他功能正常，但执行rails test时出现LoadError，提示无法加载arel/visitors/mysql。已尝试卸载arel和activerecord gem后重新执行bundle install，问题仍未解决。

报错信息 #

MyApp$ rails test
/usr/share/rvm/gems/ruby-2.5.7/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:33:in `require': cannot load such file -- arel/visitors/mysql (LoadError)
from /usr/share/rvm/gems/ruby-2.5.7/gems/activesupport-5.2.4/lib/active_support/dependencies.rb:291:in `block in require'
from /usr/share/rvm/gems/ruby-2.5.7/gems/activesupport-5.2.4/lib/active_support/dependencies.rb:257:in `load_dependency'
from /usr/share/rvm/gems/ruby-2.5.7/gems/activesupport-5.2.4/lib/active_support/dependencies.rb:291:in `require'
from /usr/share/rvm/gems/ruby-2.5.7/gems/arel-9.0.0/lib/arel/visitors.rb:7:in `<top (required)>'
from /usr/share/rvm/gems/ruby-2.5.7/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `require'
from /usr/share/rvm/gems/ruby-2.5.7/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `block in require_with_bootsnap_lfi'
from /usr/share/rvm/gems/ruby-2.5.7/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/loaded_features_index.rb:92:in `register'
from /usr/share/rvm/gems/ruby-2.5.7/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:21:in `require_with_bootsnap_lfi'
from /usr/share/rvm/gems/ruby-2.5.7/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:30:in `require'
from /usr/share/rvm/gems/ruby-2.5.7/gems/activesupport-5.2.4/lib/active_support/dependencies.rb:291:in `block in require'
from /usr/share/rvm/gems/ruby-2.5.7/gems/activesupport-5.2.4/lib/active_support/dependencies.rb:257:in `load_dependency'
from /usr/share/rvm/gems/ruby-2.5.7/gems/activesupport-5.2.4/lib/active_support/dependencies.rb:291:in `require'
from /usr/share/rvm/gems/ruby-2.5.7/gems/arel-9.0.0/lib/arel.rb:17:in `<top (required)>'
from /usr/share/rvm/gems/ruby-2.5.7/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `require'
from /usr/share/rvm/gems/ruby-2.5.7/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `block in require_with_bootsnap_lfi'
from /usr/share/rvm/gems/ruby-2.5.7/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/loaded_features_index.rb:92:in `register'
from /usr/share/rvm/gems/ruby-2.5.7/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:21:in `require_with_bootsnap_lfi'
from /usr/share/rvm/gems/ruby-2.5.7/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:30:in `require'
from /usr/share/rvm/gems/ruby-2.5.7/gems/activesupport-5.2.4/lib/active_support/dependencies.rb:291:in `block in require'
from /usr/share/rvm/gems/ruby-2.5.7/gems/activesupport-5.2.4/lib/active_support/dependencies.rb:257:in `load_dependency'
from /usr/share/rvm/gems/ruby-2.5.7/gems/activesupport-5.2.4/lib/active_support/dependencies.rb:291:in `require'
from /usr/share/rvm/gems/ruby-2.5.7/gems/activerecord-5.2.4/lib/active_record.rb:29:in `<top (required)>'
from /usr/share/rvm/gems/ruby-2.5.7/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `require'
from /usr/share/rvm/gems/ruby-2.5.7/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `block in require_with_bootsnap_lfi'
from /usr/share/rvm/gems/ruby-2.5.7/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/loaded_features_index.rb:92:in `register'
from /usr/share/rvm/gems/ruby-2.5.7/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:21:in `require_with_bootsnap_lfi'
from /usr/share/rvm/gems/ruby-2.5.7/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:30:in `require'
from /usr/share/rvm/gems/ruby-2.5.7/gems/activesupport-5.2.4/lib/active_support/dependencies.rb:291:in `block in require'
from /usr/share/rvm/gems/ruby-2.5.7/gems/activesupport-5.2.4/lib/active_support/dependencies.rb:257:in `load_dependency'
from /usr/share/rvm/gems/ruby-2.5.7/gems/activesupport-5.2.4/lib/active_support/dependencies.rb:291:in `require'
from /usr/share/rvm/gems/ruby-2.5.7/gems/activerecord-5.2.4/lib/active_record/railtie.rb:3:in `<top (required)>'
from /usr/share/rvm/gems/ruby-2.5.7/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `require'
from /usr/share/rvm/gems/ruby-2.5.7/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `block in require_with_bootsnap_lfi'
from /usr/share/rvm/gems/ruby-2.5.7/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/loaded_features_index.rb:92:in `register'
from /usr/share/rvm/gems/ruby-2.5.7/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:21:in `require_with_bootsnap_lfi'
from /usr/share/rvm/gems/ruby-2.5.7/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:30:in `require'
from /usr/share/rvm/gems/ruby-2.5.7/gems/activesupport-5.2.4/lib/active_support/dependencies.rb:291:in `block in require'
from /usr/share/rvm/gems/ruby-2.5.7/gems/activesupport-5.2.4/lib/active_support/dependencies.rb:257:in `load_dependency'
from /usr/share/rvm/gems/ruby-2.5.7/gems/activesupport-5.2.4/lib/active_support/dependencies.rb:291:in `require'
from /home/akhilr/Documents/Metastore/cpmetastore/cpmetastore/config/application.rb:8:in `<top (required)>'
from /usr/share/rvm/gems/ruby-2.5.7/gems/spring-2.1.0/lib/spring/application.rb:92:in `require'
from /usr/share/rvm/gems/ruby-2.5.7/gems/spring-2.1.0/lib/spring/application.rb:92:in `preload'
from /usr/share/rvm/gems/ruby-2.5.7/gems/spring-2.1.0/lib/spring/application.rb:157:in `serve'
from /usr/share/rvm/gems/ruby-2.5.7/gems/spring-2.1.0/lib/spring/application.rb:145:in `block in run'
from /usr/share/rvm/gems/ruby-2.5.7/gems/spring-2.1.0/lib/spring/application.rb:139:in `loop'
from /usr/share/rvm/gems/ruby-2.5.7/gems/spring-2.1.0/lib/spring/application.rb:139:in `run'
from /usr/share/rvm/gems/ruby-2.5.7/gems/spring-2.1.0/lib/spring/application/boot.rb:19:in `<top (required)>'
from /usr/share/rvm/rubies/ruby-2.5.7/lib/ruby/site_ruby/2.5.0/rubygems/core_ext/kernel_require.rb:54:in `require'
from /usr/share/rvm/rubies/ruby-2.5.7/lib/ruby/site_ruby/2.5.0/rubygems/core_ext/kernel_require.rb:54:in `require'
from -e:1:in `<main>'

解决步骤 #

• 检查数据库配置与依赖：确认config/database.yml中使用的是mysql2适配器，同时Gemfile里已添加gem 'mysql2'，执行bundle install确保依赖安装完整。
• 清理Bootsnap缓存：执行命令bundle exec rails tmp:clear，或者手动删除项目根目录下的tmp/cache文件夹，清除缓存后再尝试运行测试。
• 指定兼容的Arel版本：Rails 5.2.4默认依赖的Arel版本为8.x，当前使用的9.0.0存在兼容性问题。在Gemfile中添加gem 'arel', '~> 8.0'，然后执行bundle update arel更新依赖。
• 重置Gem依赖：删除项目根目录下的Gemfile.lock文件，执行bundle install重新安装所有依赖，确保版本匹配。
• 确认RVM环境：执行rvm use 2.5.7切换到正确的Ruby版本，再重新执行bundle install和rails test。

内容的提问来源于stack exchange，提问作者Akhil S R