Sneaking invalid values past Rails' inclusion validation

rails_inclusion_validation_trickery.rb

unless File.exist?('Gemfile')
  File.write('Gemfile', <<-GEMFILE)
    source 'https://rubygems.org'
    gem 'rails', github: 'rails/rails'
    gem 'arel', github: 'rails/arel'
    gem 'sqlite3'
  GEMFILE

  system 'bundle'
end

require 'bundler'
Bundler.setup(:default)

require 'active_record'
require 'minitest/autorun'
require 'logger'

# This connection will do for database-independent bug reports.
ActiveRecord::Base.establish_connection(adapter: 'sqlite3', database: ':memory:')
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :games do |t|
    t.integer :score
  end
end

Game = Class.new(ActiveRecord::Base)

class Crap
  def to_i
    0
  end
end

class InclusionValidationTest < Minitest::Test
  def teardown
    Game.clear_validators!
  end
  def test_invalid_with_nearby_float
    Game.validates_inclusion_of(:score, in: [0, 1])
    assert Game.new(score: 1.1).invalid?, "1.1 isn't in the list"
  end

  def test_invalid_with_nonsense_string
    Game.validates_inclusion_of(:score, in: [0, 1])
    assert Game.new(score: 'apple').invalid?, "'apple' isn't in the list"
  end

  def test_invalid_with_crap_object
    Game.validates_inclusion_of(:score, in: [0, 1])
    assert Game.new(score: Crap.new).invalid?, "There's no crap in the list"
  end
end

class InclusionInArrayWithOnlyIntegerValidationTest < Minitest::Test
  def test_invalid_with_nonsense_string
    Game.validates_numericality_of(:score, only_integer: true)
    Game.validates_inclusion_of(:score, in: [0, 1])

    game = Game.new(score: 'apple')
    game.valid?
    assert game.errors.added?(:score, :not_a_number)
    assert game.errors.added?(:score, :inclusion), "Expected an inclusion error."
  end
end