ruby​​-rspec、TypeErrorの引き上げを処理する方法は？

Question

私は温度変換を行う方法を持っています。
このメソッドは、場合によってはTypeErrorを発生させることを目的としています。
rspecでどうすれば確認できますか？

Failures: 

    1) It should raise TypeError for unknown conversion type 'blob_to_blob' should raise a TypeError when what_to_what param has the value 'blob_to_blob' 
    Failure/Error: raise TypeError 
    TypeError: 
     TypeError 
    # ./converter_spec.rb:7:in `converter' 
    # ./converter_spec.rb:25 

Finished in 0.00134 seconds 
3 examples, 1 failure 

コード：

def converter(temperature,what_to_what) 
    if what_to_what == 'farenheit_to_centigrade' 
    (temperature-32)/2 
    elsif what_to_what == 'centigrade_to_farenheit' 
    (temperature*2)+ 32 
    else 
    raise TypeError 
    end 
end 

describe "It should be able to convert farenheit to centigrade" do 
     it "should convert 50 to 9" do 
      converter(50, 'farenheit_to_centigrade').should == 9 
     end 
end 

describe "It should be able to convert centigrade to farenheit" do 
     it "should convert 9 to 50" do 
      converter(9, 'centigrade_to_farenheit').should == 50 
     end 
end 

describe "It should raise TypeError for unknown conversion type 'blob_to_blob'" do 
     it "should raise a TypeError when what_to_what param has the value 'blob_to_blob'" do 
      converter(9, 'blob_to_blob').should raise TypeError 
     end 
end 

Answer 1

期待{TypeErrorを発生させ}が提起.TOはTypeError

は今のところ以下のコードは私を与えます