Ok steps to reproduce this:

prompt> rails test_app
prompt> cd test_app
prompt> script/generate model event_service published:boolean

then go into the migration and add not null and default published to false:

class CreateEventServices < ActiveRecord::Migration
  def self.up
    create_table :event_services do |t|
      t.boolean :published, :null => false, :default => false
      t.timestamps
    end
  end

  def self.down
    drop_table :event_services
  end
end

now migrate your changes and run your tests:

prompt>rake db:migrate
prompt>rake

You should get no errors at this time. Now edit the model so that you validate_presence_of published:

class EventService < ActiveRecord::Base
  validates_presence_of :published
end

Now edit the unit test event_service_test.rb:

require 'test_helper'

class EventServiceTest < ActiveSupport::TestCase
  test "the truth" do
    e = EventServer.new
    e.published = false
    assert e.valid?
  end
end

and run rake:

prompt>rake

You will get an error in the test. Now set e.published to true and rerun the test. IT WORKS! I think this probably has something to do with the field being boolean but I can't figure it out. Is this a bug in rails? or am I doing something wrong?