Ruby on rails Rails 2.3.18由于加载错误，单元测试失败

我在Ruby2.1.5p273上运行RubyonRails2.3.18应用程序，当我运行单元测试套件时，我在终端中得到这个输出

dminca@dev:$ bundle exec rake test:units                                                                                                                                                                                                                           
* ruby 2.1.5p273 (2014-11-13 revision 48405) [x86_64-linux]
* /home/dminca/.rvm/gems/ruby-2.1.5/bin/rake
* pid: 32205
* Using RAILS_ENV for ENV_CONFIG: development
* configuring for environment: development
* loaded .env .env.development
* configuring LOGGING: file
  LOG_FILE: development.log
  LOG_PATH: log
  LOG_FILE_PATH: /home/dminca/Projects/mld/application/log/development.log
  LOG_LEVEL: debug
* configuring TRACKER: Utility::Tracker::Stdout
/home/dminca/.rvm/rubies/ruby-2.1.5/bin/ruby -I"lib:test" -I"/home/dminca/.rvm/gems/ruby-2.1.5/gems/rake-0.9.6/lib" "/home/dminca/.rvm/gems/ruby-2.1.5/gems/rake-0.9.6/lib/rake/rake_test_loader.rb" "test/unit/**/*_test.rb" 
/home/dminca/Projects/mld/application/test/unit/helpers/cms/app_texts_helper_test.rb:1:in `require': cannot load such file -- test_helper (LoadError)
        from /home/dminca/Projects/mld/application/test/unit/helpers/cms/app_texts_helper_test.rb:1:in `<top (required)>'
        from /home/dminca/.rvm/gems/ruby-2.1.5/gems/rake-0.9.6/lib/rake/rake_test_loader.rb:10:in `require'
        from /home/dminca/.rvm/gems/ruby-2.1.5/gems/rake-0.9.6/lib/rake/rake_test_loader.rb:10:in `block (2 levels) in <main>'
        from /home/dminca/.rvm/gems/ruby-2.1.5/gems/rake-0.9.6/lib/rake/rake_test_loader.rb:9:in `each'
        from /home/dminca/.rvm/gems/ruby-2.1.5/gems/rake-0.9.6/lib/rake/rake_test_loader.rb:9:in `block in <main>'
        from /home/dminca/.rvm/gems/ruby-2.1.5/gems/rake-0.9.6/lib/rake/rake_test_loader.rb:4:in `select'
        from /home/dminca/.rvm/gems/ruby-2.1.5/gems/rake-0.9.6/lib/rake/rake_test_loader.rb:4:in `<main>'
rake aborted!
Command failed with status (1): [ruby -I"lib:test" -I"/home/dminca/.rvm/gems/ruby-2.1.5/gems/rake-0.9.6/lib" "/home/dminca/.rvm/gems/ruby-2.1.5/gems/rake-0.9.6/lib/rake/rake_test_loader.rb" "test/unit/**/*_test.rb" ]
/home/dminca/.rvm/gems/ruby-2.1.5/bin/ruby_executable_hooks:15:in `eval'
/home/dminca/.rvm/gems/ruby-2.1.5/bin/ruby_executable_hooks:15:in `<main>'
Tasks: TOP => test:units
(See full trace by running task with --trace)

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如何使测试正常工作？

Rails 3.0于2010年8月发布。Rails 5.0即将发布。Rails 2.3上一次安全更新是在大约三年前，比上一次Windows XP安全补丁更新的时间要长。你考虑过更新吗？是的，我已经考虑过升级，但是自从2010以来，这个应用程序已经大规模开发，它是巨大的，而且没有任何书面测试来帮助升级。我想先让测试套件工作，然后我可以考虑升级到一个更高的版本。我建议先在Ruby 1.87上运行它，然后尝试在Ruby 2。x版本上运行Rails 2.3。请参阅及其答案。应用程序在Ruby 2.1.5上运行正常，没有兼容性问题。为使其在此版本上正常工作，已应用了一个次要修复程序。