如何通过rspec测试

Question

我正在尝试使用测试驱动开发创建游戏Mastermind。我在解决如何通过这个特定测试时遇到了问题：

it "should valiate secret contains four accepted uppercase characters" do
            @game.secret = "XXXX"
            secret = "RRRR"
            valid1 = @game.checksecret(secret)
            valid2 = check_valid(secret)
            valid1.should == valid2 && @game.secret.should == secret && valid1.should == 0
end

这是我目前的代码：

def checksecret(secret)
        secret = "RRRR"
        valid1 = secret
        valid2 = check_valid(secret)
        valid1.should == valid2 && secret.should == secret && valid1.should == 0
end 

这是我收到的错误消息。

1) OXs_Game::Game#Mastermind game should valiate secret contains four accepted uppercase characters
 Failure/Error: @game.secret = secret

 NoMethodError:
   undefined method `secret=' for nil:NilClass
 # ./wad_mastermind_spec_01.rb:13:in `check_valid'
 # ./wad_mastermind_gen_01.rb:61:in `checksecret'
 # ./wad_mastermind_spec_01.rb:92:in `block (3 levels) in <module:OXs_Game>'

我觉得我试图以错误的方式解决它，但无法弄清楚我应该如何解决问题。