From: Ryan Davis <ryand-ruby@...>
Date: 2010-05-27T06:49:09+09:00
Subject: Re: How do I write an RSpec test to unit-test this interesting  metaprogramming code?


On May 23, 2010, at 07:00 , James Wenton wrote:

> So far, so good. I want to write some RSpec tests to verify this code
> is actually doing what it's supposed to. But there's a problem! If I
> invoke `attr_option :foo` in one of the test methods, that method is
> now forever defined in Config. So a subsequent test will fail when it
> shouldn't, because `foo` is already defined:
> 
>      it "should support a specified option" do
>        c = Configurator::Config
>        c.attr_option :foo
>        # ...
>      end
> 
>      it "should support multiple options" do
>        c = Configurator::Config
>        c.attr_option :foo, :bar, :baz   # Error! :foo already defined
>                                         # by a previous test.
>        # ...
>      end

Caleb and Robert are nit-picking... 'c' is a perfectly fine name for a variable in a 4 line test/spec.

The problem you're having is easily solved by using anonymous subclasses:

     it "should support a specified option" do
       c = Class.new(Configurator::Config)
       c.attr_option :foo
       # ...
     end

That makes a throwaway class that has all the same features of the superclass without any of the infectious properties of calling your attr methods on the real thing.