`validation_errors` throws error when there are no errors

[happycollision]

If you invoke the validation_errors method when your response has no errors, you get an error. Which is about 5 hours worth of confusing.

Take the following as an example:

RSpec.describe "reservations#create", type: :request do
  subject(:make_request) do
    jsonapi_post "/api/v1/reservations", payload
  end

  describe 'basic create' do
    let!(:patron) { create(:patron) }
    let(:payload) do
      {
        data: {
          type: 'reservations',
          relationships: {
            patron: {
              data: { type: 'patrons', id: patron.id.to_s }
            }
          }
        }
      }
    end

    it 'creates the resource with valid params' do
      make_request
      expect(validation_errors).to be_empty
    end
  end
end

If your data is bad—like if I just omit the relationships part of the payload above—you get a helpful message:

1) reservations#create basic create creates the resource with valid params                                                  
     Failure/Error: expect(validation_errors).to be_empty      
       expected `{:patron=>"must exist"}.empty?` to return true, got false 

But once you have actual, valid data, you get this:

  1) reservations#create basic create creates the resource with valid params                                                  
     Failure/Error: expect(validation_errors).to be_empty      
                                                               
     NoMethodError:                                            
       undefined method `each' for nil:NilClass

If you write your test like this is passes just fine.

    it 'creates the resource with valid params' do
      make_request
      expect(json['errors']).to be_nil
    end

And just for grins, if you add one single line like this...

    it 'creates the resource with valid params' do
      make_request
      puts validation_errors
      expect(json['errors']).to be_nil
    end

Boom. Failure.

[happycollision]

I thought that GitHub would close this automatically. Guess I didn't word something correctly.