install_gem.rb

      def run
        command = "gem install #{gemspec_helper.gem_path}"
        output.puts "Executing #{command.inspect}:"

        sh sudo_wrapper(command) # TODO where does sh actually come from!? - rake, apparently
      end

      def sudo_wrapper(command)
        if use_sudo?
          "sudo #{command}"
        else
          command
        end
      end

      def use_sudo?
        if host_os =~ /mswin|windows|cygwin/i
          false
        else
          true
        end
        
      end

      def host_os
        Config::CONFIG['host_os']
      end

test_install_gem.rb

      rubyforge_command_context "running" do
        setup do
          stub(@gemspec_helper).gem_path { 'pkg/zomg-1.1.1.gem' } 
          stub(@command).sudo_wrapper { 'sudo gem install pkg/zomg-1.1.1.gem' }
          stub(@command).sh

          @command.run
        end

        should "call sudo wrapper with gem install" do
          assert_received(@command) {|command| command.sudo_wrapper('gem install pkg/zomg-1.1.1.gem') }
        end

        should "call sh with output of sudo wrapper" do
          assert_received(@command) {|command| command.sh 'sudo gem install pkg/zomg-1.1.1.gem' }
        end
      end

      rubyforge_command_context "use_sudo?" do
        should "be false on mswin" do
          stub(@command).host_os { "i386-mswin32" }
          assert ! @command.use_sudo?
        end

        should "be false on windows" do
          stub(@command).host_os { "windows" }
          assert ! @command.use_sudo?
        end

        should "be false on cygwin" do
          stub(@command).host_os { "cygwin" }
          assert ! @command.use_sudo?
        end

        should "be true on basically anything else" do
          stub(@command).host_os { "darwin9" }
          assert @command.use_sudo?
        end
      end

      rubyforge_command_context "sudo_wrapper" do
        should "prefix sudo if needed" do
          stub(@command).use_sudo? { true }
          assert_equal "sudo blarg", @command.sudo_wrapper("blarg")
        end

        should "not prefix with sudo if unneeded" do
          stub(@command).use_sudo? { false }
          assert_equal "blarg", @command.sudo_wrapper("blarg")
        end
      end