Watir问题--LoadError: cannot load such file -- watir-classic

在执行下面程序，报错

require 'watir'
ie=page = Watir::Browser.new :ie
ie.goto "www.google.com"

报的错误：

C:Userszxy>irb
DL is deprecated, please use Fiddle
irb(main):001:0> require "watir"
=> true
irb(main):002:0> ie=page = Watir::Browser.new :ie
LoadError: cannot load such file -- watir-classic
        from C:/Ruby200-x64/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:53:in `require'
        from C:/Ruby200-x64/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:53:in `require'
        from C:/Ruby200-x64/lib/ruby/gems/2.0.0/gems/watir-5.0.0/lib/watir/loader.rb:41:in `load_dri
ver'
        from C:/Ruby200-x64/lib/ruby/gems/2.0.0/gems/watir-5.0.0/lib/watir/loader.rb:33:in `load_dri
ver_for'
        from C:/Ruby200-x64/lib/ruby/gems/2.0.0/gems/watir-5.0.0/lib/watir/loader.rb:6:in `initializ
e'
        from (irb):2:in `new'
        from (irb):2
        from C:/Ruby200-x64/bin/irb:12:in `<main>'
irb(main):003:0> exit

原因分析：是由于Watir::Browser 是在watir-webdriver模块中

解决办法，在程序中引入 watir-webdriver 模块就ok了，加入watir-webdriver模块后的代码如下：

require 'watir'
require 'watir-webdriver'
ie=page = Watir::Browser.new :ie
ie.goto "www.google.com"