Rails4 Scaffold test fails, how can I figure out the reason?

Question

I generated scaffold application with Post resource.

Here is the test code

  describe "GET index" do
    it "assigns all posts as @posts" do
      post = Post.create! valid_attributes
      get :index, {}, valid_session
      assigns(:posts).should eq([post])
    end
  end

Here is implementation of posts#index

  # GET /posts
  # GET /posts.json
  def index
    @posts = Post.all
  end

Seems legit, however I keep getting this error when running rspec I'd be really glad if you could give me any tips.

Failures:

  1) PostsController GET index assigns all posts as @posts
     Failure/Error: assigns(:posts).should eq([post])

       expected: [#<Post id: 23, body: "MyString", created_at: "2013-07-08 15:59:47", updated_at: "2013-07-08 15:59:47">]
            got: #<ActiveRecord::Relation [#<Post id: 1, body: nil, created_at: "2013-07-08 15:58:08", updated_at: "2013-07-08 15:58:08">, #<Post id: 2, body: "MyString", created_at: "2013-07-08 15:58:08", updated_at: "2013-07-08 15:58:08">, #<Post id: 3, body: "MyString", created_at: "2013-07-08 15:58:08", updated_at: "2013-07-08 15:58:08">, #<Post id: 4, body: "MyString", created_at: "2013-07-08 15:58:08", updated_at: "2013-07-08 15:58:08">, #<Post id: 7, body: "MyString", created_at: "2013-07-08 15:58:08", updated_at: "2013-07-08 15:58:08">, #<Post id: 8, body: "MyString", created_at: "2013-07-08 15:58:08", updated_at: "2013-07-08 15:58:08">, #<Post id: 9, body: "MyString", created_at: "2013-07-08 15:58:08", updated_at: "2013-07-08 15:58:08">, #<Post id: 10, body: "MyString", created_at: "2013-07-08 15:58:08", updated_at: "2013-07-08 15:58:08">, #<Post id: 11, body: "MyString", created_at: "2013-07-08 15:58:08", updated_at: "2013-07-08 15:58:08">, #<Post id: 12, body: "MyString", created_at: "2013-07-08 15:58:08", updated_at: "2013-07-08 15:58:08">, ...]>

       (compared using ==)

       Diff:
       @@ -1,2 +1,22 @@
       -[#<Post id: 23, body: "MyString", created_at: "2013-07-08 15:59:47", updated_at: "2013-07-08 15:59:47">]
       +[#<Post id: 1, body: nil, created_at: "2013-07-08 15:58:08", updated_at: "2013-07-08 15:58:08">,
       + #<Post id: 2, body: "MyString", created_at: "2013-07-08 15:58:08", updated_at: "2013-07-08 15:58:08">,
       + #<Post id: 3, body: "MyString", created_at: "2013-07-08 15:58:08", updated_at: "2013-07-08 15:58:08">,
       + #<Post id: 4, body: "MyString", created_at: "2013-07-08 15:58:08", updated_at: "2013-07-08 15:58:08">,
       + #<Post id: 7, body: "MyString", created_at: "2013-07-08 15:58:08", updated_at: "2013-07-08 15:58:08">,
       + #<Post id: 8, body: "MyString", created_at: "2013-07-08 15:58:08", updated_at: "2013-07-08 15:58:08">,
       + #<Post id: 9, body: "MyString", created_at: "2013-07-08 15:58:08", updated_at: "2013-07-08 15:58:08">,
       + #<Post id: 10, body: "MyString", created_at: "2013-07-08 15:58:08", updated_at: "2013-07-08 15:58:08">,
       + #<Post id: 11, body: "MyString", created_at: "2013-07-08 15:58:08", updated_at: "2013-07-08 15:58:08">,
       + #<Post id: 12, body: "MyString", created_at: "2013-07-08 15:58:08", updated_at: "2013-07-08 15:58:08">,
       + #<Post id: 13, body: "MyString", created_at: "2013-07-08 15:58:08", updated_at: "2013-07-08 15:58:08">,
       + #<Post id: 14, body: "MyString", created_at: "2013-07-08 15:58:08", updated_at: "2013-07-08 15:58:08">,
       + #<Post id: 15, body: nil, created_at: "2013-07-08 15:59:47", updated_at: "2013-07-08 15:59:47">,
       + #<Post id: 16, body: "MyString", created_at: "2013-07-08 15:59:47", updated_at: "2013-07-08 15:59:47">,
       + #<Post id: 17, body: "MyString", created_at: "2013-07-08 15:59:47", updated_at: "2013-07-08 15:59:47">,
       + #<Post id: 18, body: "MyString", created_at: "2013-07-08 15:59:47", updated_at: "2013-07-08 15:59:47">,
       + #<Post id: 19, body: "MyString", created_at: "2013-07-08 15:59:47", updated_at: "2013-07-08 15:59:47">,
       + #<Post id: 20, body: "MyString", created_at: "2013-07-08 15:59:47", updated_at: "2013-07-08 15:59:47">,
       + #<Post id: 21, body: "MyString", created_at: "2013-07-08 15:59:47", updated_at: "2013-07-08 15:59:47">,
       + #<Post id: 22, body: "MyString", created_at: "2013-07-08 15:59:47", updated_at: "2013-07-08 15:59:47">,
       + #<Post id: 23, body: "MyString", created_at: "2013-07-08 15:59:47", updated_at: "2013-07-08 15:59:47">]

     # ./spec/controllers/posts_controller_spec.rb:41:in `block (3 levels) in <top (required)>'

Answer 1

There are two reasons why your test is failing. First, you're getting an ActiveRecord::Relation rather than an Array back from assigns(:posts) . Second, there appear to be 22 posts that have already been created by the time this test is run.

The first difference is due to a Rails 4 change to Model.all which now returns an ActiveRecord::Relation rather than an Array , as described in http://edgeguides.rubyonrails.org/4_0_release_notes.html .

I can't explain why there are pre-existing posts. Based on the timestamps, they seem to have been created just prior to this test. Do other post-creating tests execute prior to this? Have you turned off transactions?