snippet.rb

require 'rake/gempackagetask'

class Gem::Specification
  attribute :wiki
  attribute :bugtracker
end

SPEC = Gem::Specification.new do |s|
  s.name          = "gemspec-test"
  s.summary       = "Testing a gemspec"
  s.version       = "1.0"
  s.wiki          = "http://example.com/wiki"
  s.bugtracker    = "http://example.com/tracker"
end

Rake::GemPackageTask.new(SPEC) {|pkg| pkg.gem_spec = SPEC }

task :test => :package do
  format = Gem::Format.from_file_by_path(File.join('pkg', SPEC.full_name + '.gem'))
  puts "Wiki:       " + format.spec.wiki
  puts "Bugtracker: " + format.spec.bugtracker
end