“gem install autotest-fsevent” -v 0.1.1 fails on snow leopard

Question

Following Michael Hartl's Rails 2.3 tutorial. Excellent, so far, but I am stuck on the prep for the testing environment on page 87. Can't get the autotest-fsevent to install.

iMac i7 running Snow Leopard.

Typing the command in the Title, above, I get the following error message:

bash-3.2$ sudo gem install autotest-fsevent -v 0.1.1 Building native extensions. This could take a while... ERROR: Error installing autotest-fsevent: ERROR: Failed to build gem native extension.

    /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby extconf.rb

mkmf.rb can't find header files for ruby at /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/ruby.h

Gem files will remain installed in /Library/Ruby/Gems/1.8/gems/sys-uname-0.8.6 for inspection. Results logged to /Library/Ruby/Gems/1.8/gems/sys-uname-0.8.6/ext/gem_make.out

I've tried downloading a ruby 1.8.7 fresh install to get the header files, but that has not seemed to work. Copied them to the path in bold, above.

Any help will be greatly appreciated.

-lloyd