前もって感謝します。
Cygwin で Rails を実行しています。レールコンソールを除いて、すべてがうまく機能するように見えます。コンソールを実行したいとき、これは私が得るエラーです：
$ rails console
/usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:239:in `require': cannot load such file -- minitest/unit (LoadError)
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:239:in `block in require'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:225:in `block in load_dependency'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:591:in `new_constants_in'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:225:in `load_dependency'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:239:in `require'
from /usr/lib/ruby/1.9.1/test/unit/assertions.rb:1:in `<top (required)>'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:239:in `require'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:239:in `block in require'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:225:in `block in load_dependency'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:591:in `new_constants_in'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:225:in `load_dependency'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:239:in `require'
from /usr/lib/ruby/1.9.1/test/unit/testcase.rb:1:in `<top (required)>'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:239:in `require'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:239:in `block in require'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:225:in `block in load_dependency'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:591:in `new_constants_in'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:225:in `load_dependency'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:239:in `require'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/test_case.rb:1:in `<top (required)>'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:239:in `require'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:239:in `block in require'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:225:in `block in load_dependency'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:591:in `new_constants_in'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:225:in `load_dependency'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:239:in `require'
from /usr/lib/ruby/gems/1.9.1/gems/railties-3.0.0/lib/rails/console/app.rb:2:in `<top (required)>'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:239:in `require'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:239:in `block in require'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:225:in `block in load_dependency'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:591:in `new_constants_in'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:225:in `load_dependency'
from /usr/lib/ruby/gems/1.9.1/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:239:in `require'
from /usr/lib/ruby/gems/1.9.1/gems/railties-3.0.0/lib/rails/application.rb:225:in `initialize_console'
from /usr/lib/ruby/gems/1.9.1/gems/railties-3.0.0/lib/rails/application.rb:153:in `load_console'
from /usr/lib/ruby/gems/1.9.1/gems/railties-3.0.0/lib/rails/commands/console.rb:26:in `start'
from /usr/lib/ruby/gems/1.9.1/gems/railties-3.0.0/lib/rails/commands/console.rb:8:in `start'
from /usr/lib/ruby/gems/1.9.1/gems/railties-3.0.0/lib/rails/commands.rb:23:in `<top (required)>'
from script/rails:6:in `require'
from script/rails:6:in `<main>'
どんな助けでも大歓迎です