Ruby on rails rspec destroy count fails - ruby-on-rails

Question

I've written some tests for simple application. I'm having problem with #destroy method in my authors_controller. As I've done this from some tutorials (many sources shows similar approach) I guess it should work, but such error occurs:
Failure/Error: expect { delete :destroy, id: author.id }.to change(Author, :count).by(-1) expected #count to have changed by -1, but was changed by 0
Here's my code:
author_controller_spec.rb
require 'rails_helper'
describe AuthorsController do
let(:author) { FactoryGirl.create(:author) }
describe 'DELETE #destroy' do
it 'deletes author' do
expect { delete :destroy, id: author.id }.to change(Author, :count).by(-1)
end
end
end
authors_controller.rb
class AuthorsController < ApplicationController
def show
#author = Author.find(params[:id])
end
def new
#author = Author.new
end
def create
#author = Author.new(author_params)
if #author.save
redirect_to #author
else
render 'new'
end
end
def edit
#author = Author.find(params[:id])
end
def update
#author = Author.find(params[:id])
if #author.update(author_params)
redirect_to #author
else
render 'edit'
end
end
def destroy
#author = Author.find(params[:id])
#author.books.each do |book|
book.destroy if book.authors.count == 1
end
#author.destroy
redirect_to authors_path
end
def index
#author = Author.all
end
private
def author_params
params.require(:author).permit(:name, :surname, book_ids: [])
end
end

Answer 1

The let call is not made until the first time you mention the variable, as it's lazy evaluation. This means that within your expect block, you are both creating and destroying the record, leading to an overall change of 0.
Either create the author outside of the block:
describe AuthorsController do
let(:author) { FactoryGirl.create(:author) }
describe 'DELETE #destroy' do
author
it 'deletes author' do
expect { delete :destroy, id: author.id }.to change(Author, :count).by(-1)
end
end
end
Or, tell the let block not to evaluate lazily by using let!:
describe AuthorsController do
let!(:author) { FactoryGirl.create(:author) }
describe 'DELETE #destroy' do
it 'deletes author' do
expect { delete :destroy, id: author.id }.to change(Author, :count).by(-1)
end
end
end