event.rb

class Event < Ohm::Model

KINDS = %w[creation approval disapproval reception delivery]

reference :user, lambda { |id| User.find(id)}
reference :item, lambda { |id| id.nil? ? nil : Item.find(id)}
reference :transaction, lambda { |id| id.nil? ? nil : Transaction.find(id)}

attribute :kind
attribute :text
attribute :created_at

index :user
index :item
index :transaction


def validate
  assert_present :kind
  assert_present :text
  #KINDS = %w[creation approval disapproval reception delivery]
  assert KINDS.include?(self.kind), [:kind, :not_valid]
  #cheap before_create hook
  self.created_at = Time.now
end


end

event_test.rb

require 'test_helper'

class EventTest < ActiveSupport::TestCase


  # Replace this with your real tests.
  test "a event should have a text" do
    e = Event.new(:kind => "creation")
    assert_false e.valid?
  end

  test "a event should have a kind" do
    e = Event.new(:text => "Hola, manola")
    assert_false e.valid?
  end

  test "a event should have a kind and text" do
    e = Event.new(:text => "Hola, manola", :kind => "creation")
    assert e.valid?
  end

  test "a event kind should be within defined list" do
    Event::KINDS.each do |kind|
      e = Event.new(:text => "Hola, manola", :kind => kind)
      assert e.valid?
    end
  end

  test "a event kind should not be different than the ones defined in list" do
    wrong_kind = "pinga"
    assert_false Event::KINDS.include? wrong_kind
    e = Event.new(:text => "Hola, manola", :kind => wrong_kind)
    assert_false e.valid?
    assert_equal e.errors, [[:kind, :not_valid]]
  end

end