Add virtual recipe support

[geraud]

This patch enables the creation of inlined virtual recipes. It is useful to test definitions.

runner = ChefSpec::Runner.new    
runner.define_recipe('cookbook::virtual_recipe') do
  mydefinition 'test' do
    ...
  end    
end

runner.converge('cookbook::virtual_recipe')

or

runner = ChefSpec::Runner.new    
runner.converge_virtual_recipe('cookbook') do
  mydefinition 'test' do
    ...
  end    
end

[sethvargo]

Ohai @geraud. Thank you for the Pull Request. Unfortunately this is not a feature I want to support in ChefSpec. The notion of creating virtual recipes is cool, but the general best practice for testing definitions (and LWRPs) it to make a separate cookbook (like mycookbook_test) that has recipes utilizing the definition. These "fixtures" can be shared with other testing frameworks, like Test Kitchen.

[geraud]

Ok, no problem.

[sethvargo]

I feel bad, but this is a fairly large feature to support and comes with many edge cases to test. Might I suggest writing a blog post about this pattern? I can link to it in the README.

[geraud]

Don't worry about it, I will just use a monkey patch.