ActiveModel::MissingAttributeError: can't write unknown attribute `ad_id' with FactoryGirl

When you say:

has_one :image

Rails expects you to define an ad_id field at the images table. Given the way your associations are organised, I assume you have an image_id and a logo_id a the ads table so instead of:

class Ad < ActiveRecord::Base
  belongs_to :page

  has_one :image
  has_one :logo
end

You probably mean:

class Ad < ActiveRecord::Base
  belongs_to :page
  belongs_to :image
  belongs_to :logo
end

If that's not the case then you need to add ad_id columns to both Image and Logo.

I ran into this same error and it took a while to figure out a fix. Just in case this helps someone else in the future, here's my scenario and what worked for me. Class names have been changed as this is for work:

I had 2 namespaced models:

Pantry::Jar
has_many :snacks, class_name: Pantry::Snack
accepts_nested_attributes_for :snacks

Pantry::Snack
belongs_to :pantry_jar, class_name: Pantry::Jar

When I would create a new jar with new snacks, I would get:

ActiveModel::MissingAttributeError: can't write unknown attribute `jar_id'

The fix was to change the has_many to be more explicit about the foreign key:

has_many :snacks, class_name: Pantry::Snack, foreign_key: :pantry_jar_id