Rails full test in vagrant is too slow in my laptop. Did I do something wrong?

I am trying to contribute something in rails.
For the first step, I setup rails-dev-box and configured rsync.

After that I ran my first rails test.

$>bundle exec rake test

Everything looks fine except the test time.

It took more than an hour and I stopped it manually.

I wonder how other people do the full test while developing rails.

Is there any way to speed up the full test or should I test only particular component?

Please help me to go one step forward for contributing to rails community.

Thanks in advance.

Please see
http://edgeguides.rubyonrails.org/contributing_to_ruby_on_rails.html#running-tests
.