Testing ActiveRecord models inside a gem?

Question

I'm trying to extract a set of models from a Rails 3.2.3 app into a gem so they can be used as a shared interface between applications.

I moved the model into a module and put it in lib/invite_interface/invite.rb

module InviteInterface
  class Invite < ActiveRecord::Base
    belongs_to :user
  end

  def to_json; end;
  def from_json; end;
end

I plopped rspec into the gemfile, got it running successfully, created the following spec:

require 'spec_helper'

describe InviteInterface::EncounterSurvey do
  it 'should belong to user' do
    subject.should respond_to(:user)
  end

end

Unfortunately, I can't execute rspec on the model, because active record/rspec wants an active connection.

1) InviteInterface::Invite should belong to encounter survey set
   Failure/Error: subject.should respond_to(:user)
   ActiveRecord::ConnectionNotEstablished:
     ActiveRecord::ConnectionNotEstablished
   # /Users/justin/.rbenv/versions/1.9.3-p0/lib/ruby/gems/1.9.1/gems/activerecord-3.2.3/lib/active_record/connection_adapters/abstract/connection_pool.rb:398:in `retrieve_connection'
   # /Users/justin/.rbenv/versions/1.9.3-p0/lib/ruby/gems/1.9.1/gems/activerecord-3.2.3/lib/active_record/connection_adapters/abstract/connection_specification.rb:168:in `retrieve_connection'
   # /Users/justin/.rbenv/versions/1.9.3-p0/lib/ruby/gems/1.9.1/gems/activerecord-3.2.3/lib/active_record/connection_adapters/abstract/connection_specification.rb:142:in `connection'
   # /Users/justin/.rbenv/versions/1.9.3-p0/lib/ruby/gems/1.9.1/gems/activerecord-3.2.3/lib/active_record/model_schema.rb:228:in `columns'
   # /Users/justin/.rbenv/versions/1.9.3-p0/lib/ruby/gems/1.9.1/gems/activerecord-3.2.3/lib/active_record/model_schema.rb:243:in `column_defaults'

How do I prevent ActiveRecord from looking for a DB connection?

Answer 1

You need to test your library with a database anyway, so you might as well use an in-memory SQLite database for testing. Just add this to spec_helper.rb:

ActiveRecord::Base.establish_connection(:adapter => "sqlite3", 
                                       :database => ":memory:")

and create your schema as follows:

ActiveRecord::Schema.define do
  self.verbose = false

  create_table :invites, :force => true do |t|
    t.string :text
  end
  ...
end