Rails3.0にCapybaraとlaunchyを追加

Gemfileに下記の2行を追加。

gem 'capybara'
gem 'launchy'

bundle installを実行。下記のようなエラーがでる。
bundle install
-- 省略 -- 
Installing nokogiri (1.5.0) with native extensions
Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.

/usr/local/bin/ruby extconf.rb
checking for libxml/parser.h... yes
checking for libxslt/xslt.h... no
-----
libxslt is missing.  please visit http://nokogiri.org/tutorials/installing_nokogiri.html for help with installing dependencies.
-----
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers.  Check the mkmf.log file for more
details.  You may need configuration options.

Provided configuration options:
        --with-opt-dir
        --without-opt-dir
        --with-opt-include
        --without-opt-include=${opt-dir}/include
        --with-opt-lib
        --without-opt-lib=${opt-dir}/lib
        --with-make-prog
        --without-make-prog
        --srcdir=.
        --curdir
        --ruby=/usr/local/bin/ruby
        --with-zlib-dir
        --without-zlib-dir
        --with-zlib-include
        --without-zlib-include=${zlib-dir}/include
        --with-zlib-lib
        --without-zlib-lib=${zlib-dir}/lib
        --with-iconv-dir
        --without-iconv-dir
        --with-iconv-include
        --without-iconv-include=${iconv-dir}/include
        --with-iconv-lib
        --without-iconv-lib=${iconv-dir}/lib
        --with-xml2-dir
        --without-xml2-dir
        --with-xml2-include
        --without-xml2-include=${xml2-dir}/include
        --with-xml2-lib
        --without-xml2-lib=${xml2-dir}/lib
        --with-xslt-dir
        --without-xslt-dir
        --with-xslt-include
        --without-xslt-include=${xslt-dir}/include
        --with-xslt-lib
        --without-xslt-lib=${xslt-dir}/lib


Gem files will remain installed in /usr/local/lib/ruby/gems/1.9.1/gems/nokogiri-1.5.0 for inspection.
Results logged to /usr/local/lib/ruby/gems/1.9.1/gems/nokogiri-1.5.0/ext/nokogiri/gem_make.out
An error occured while installing nokogiri (1.5.0), and Bundler cannot continue.
Make sure that `gem install nokogiri -v '1.5.0'` succeeds before bundling.

調べた結果、libxslt-develが必要らしいので、インストール。
yum install libxslt-devel

再度bundle installを実行。
bundle install
今度はうまくいった。