How to test mongoid model validations with message by shoulda?

Question

I have a model with validations, like this:

class Order
  include Mongoid::Document

  field :first_name, type: String
  field :last_name, type: String

  validates_presence_of :first_name, :message => "Can't be empty"
  validates_presence_of :last_name, :message => "Can't be empty"
end

I describe model by rspec and thoughtbot's shoulda:

describe Order do
  # validations
  it { should validate_presence_of(:first_name) }
  it { should presence_of(:last_name) }
end

But I get failures:

Failures:

  1) Order 
     Failure/Error: it { should validate_presence_of(:first_name) }
       Expected errors to include "can't be blank" when first_name is set to nil, got errors: ["first_name Can't be empty (nil)", "last_name Can't be empty (nil)"]
     # ./spec/models/order_spec.rb:10:in `block (2 levels) in <top (required)>'

Moreover 'should'-cases work very well without messages in model validations.

How to test model validations with messages?

Answer 1

mongoid-rspec gem allows to test model validations with messages.

it { should validate_uniqueness_of(:email).with_message("is already taken") }