Undefined method '+' for Rspec. What does it mean? [closed]

Question

I'm hitting a wall because I'm terribly confused about what this rspec error message means. I am testing to see whether an art piece has a cost. Here are snippets of my rspec:

let(:valid_art_piece){ { date_of_creation: DateTime.parse('2012-3-13'), 
placement_date_of_sale: DateTime.parse('2014-8-13'), cost: 250, medium: 'sculpture', 
availability: true } }

it 'requires a cost' do
  art_piece = ArtPiece.new(valid_art_piece.merge(cost: ''))
  expect(art_piece).to_not be_valid
  expect(art_piece.errors[:cost].to include "can't be blank")
end

error message:

1) ArtPiece requires a cost
 Failure/Error: expect(art_piece.errors[:cost].to include "can't be blank")
 NoMethodError:
   undefined method `+' for #<RSpec::Matchers::BuiltIn::Include:0x000001050f4cd0>
 # ./spec/models/artist_piece_spec.rb:30:in `block (2 levels) in <top (required)>'

As far as I'm concerned this shouldn't have failed and I don't know why its failing. My schema.rb has the field as null false and my model validates for it with the numericality: true option.

class ArtPiece < ActiveRecord::Base
  validates_presence_of :date_of_creation
  validates_presence_of :placement_date_of_sale
  validates :cost, numericality: true
  validates_presence_of :medium
  validates_presence_of :availability
end

I don't know what the problem is. Some help?

Answer 1

It's an syntax error. You missed the brackets before .to and before "can't be blank":

This line should looks like that:

expect(art_piece.errors[:cost] ).to include ("can't be blank")

Anyway, I suggest to replace include method using match_array

it 'requires a cost' do
  art_piece = ArtPiece.new(valid_art_piece.merge(cost: ''))
  expect(art_piece).to_not be_valid
  expect(art_piece.errors[:cost]).to match_array (["can't be blank"])
end

PS: It is good conventionto implement only one expectation per test.

Final example should looks like that:

context "art_piece" do
  subject { ArtPiece.new(valid_art_piece.merge(cost: '')) }

  it 'should_not be valid' do
     expect(subject).to_not be_valid
  end

  it 'requires a cost' do
    expect(subject.errors[:cost]).to match_array (["can't be blank"])
  end
end

hope it will help :)