Q:

Create custom rspec variable like response for controller specs

I want to create a custom variable similar to response object that should only be available in controller specs.  I noticed that rspec supports filters which are before/after hooks which means I can create instance variables with them to be used later.  But response object feels and works more like a let variable that is lazily evaluated.  Also, controller specs support assign method that can accept arguments. 
Does rspec support any way to create similar methods to be used with a specific type of spec? 
Note: I don't need to support anything below rspec 3.0. 

A:

You can simply do this by creating a module with your function and then including that in your RSpec configure block.  You can control the types of specs where this should be available as a second parameter when you include the module:
module ControllerSpecHelpers
  def something
    'fubar2000'
  end
end

RSpec.configure do |config|
  config.include ControllerSpecHelpers, type: :controller
end

RSpec.describe BlahController, type: :controller do
  it 'should be possible to use the `something` helper in a controller spec' do
    expect(something).to eq('fubar2000')
  end
end

