gistfile1.rb

require 'rubygems'
require 'rbconfig'
require 'rspec'

class PlatformDependentExample
  def platform
    case RbConfig::CONFIG['host_os']
    when /windows/
      :windows
    when /linux/
      :linux
    when /darwin/
      :macosx
    when /solaris|bsd/
      :unix
    end
  end

  def test
    platform
  end
end

RSpec.configuration.filter_run :os => :linux

describe PlatformDependentExample do

  describe '#test' do
    before :all do
      @e = PlatformDependentExample.new
    end

    it 'returns :windows if on Windows', :os => :windows do
      @e.test.should == :windows
    end

    it 'returns :linux if on Linux', :os => :linux do
      @e.test.should == :linux
    end

    it 'returns :macosx if on Mac OS X', :os => :macosx do
      @e.test.should == :macosx
    end

    it 'returns :unix if on Unix', :os => :unix do
      @e.test.should == :unix
    end
  end

end