No Instance Variables in Specs (for @Blighte)

1_explanation.md

(this started on twitter)

The microposts spec starts out with

let(:user) { FactoryGirl.create(:user) }
  before do
    # This code is wrong!
    @micropost = Micropost.new(content: "Lorem ipsum", user_id: user.id)
  end

  subject { @micropost }

Michael is telling you the code is wrong to set an instance variable in the spec. Instead, you should just:

  let(:user) { FactoryGirl.create(:user) }
  subject { Micropost.new(content: "Lorem ipsum", user_id: user.id) }

This way, the subject is set to the Micropost.new

The same happens in my Dog example... We are setting the subject to a new instance of Dog.

describe Dog do

This will set the subject to Dog.new

dog.rb

class Dog

  def initialize(name="sparky")
    @name = name
  end

  def name
    @name
  end
end

dog_spec.rb

require 'rspec'
require './dog'

describe Dog do
  it { should respond_to(:name) }
end

I understand that you are saying that I shouldn't use instance variables in the spec files. I'm still new so I don't have all of the best practices (like variable scope) down yet so I appreciate you pointing that out. Can you explain (or give a link for) why it is bad to use an instance variable in a spec file?

I'm not so sure @mhartl is saying the instance variable is the "wrong" part in that line of code though. In section 10.1.2 he says that the problem is that the user_id attribute is accessible. As far as I can tell, he repeatedly uses instance variables in his spec files in the tutorial (for the micropost model and the user model).

I definitely shouldn't have put words in Michael's mouth; I assumed what was "wrong" with the spec syntax without knowing.

IMHO, using instance variables is not as flexible as using lets.

• with nested contexts, you can easily override lets in subsequence child contexts
• a let is a call to a method, and can easily be moved to a true method if you need one
• purely aesthetic preferences

That's not why the code is wrong. Using instance variables in specs is fine, although I prefer to use let when I can. The code is wrong because setting the user_id doesn't work as soon as you define attr_accessible. Instead, you need to define the micropost through the association, using code like user.microposts.build(...), as described in Section 10.1.3.