activerecord bug?

$stdout

active record
  role built from a context
    context
      should eq #<Context id: 1, type: nil>
  role built from a role through context
    context
      should eq #<Context id: 2, type: nil> (FAILED - 1)
  student built from a program
    program
      should eq #<Program id: 3, type: "Program">
  student built from a teacher through a program
    program
      should eq #<Program id: 4, type: "Program"> (FAILED - 2)

Failures:

  1) active record role built from a role through context context 
     Failure/Error: its(:context) { should eq(context) }
       
       expected: #<Context id: 2, type: nil>
            got: nil
       
       (compared using ==)
     # ./spec/build_has_many_through_association_spec.rb:63:in `block (3 levels) in <top (required)>'

  2) active record student built from a teacher through a program program 
     Failure/Error: its(:program) { should eq(program) }
       
       expected: #<Program id: 4, type: "Program">
            got: nil
       
       (compared using ==)
     # ./spec/build_has_many_through_association_spec.rb:75:in `block (3 levels) in <top (required)>'

Finished in 0.23493 seconds
4 examples, 2 failures

Failed examples:

rspec ./spec/build_has_many_through_association_spec.rb:63 # active record role built from a role through context context 
rspec ./spec/build_has_many_through_association_spec.rb:75 # active record student built from a teacher through a program program 

Gemfile

source "https://rubygems.org"

gem "rails", :git => "https://github.com/rails/rails"
gem "sqlite3"
gem "rspec"

stdout

active record
  role built from a context
    context
      should eq #<Context id: 1, type: nil>
  role built from a role through context
    context
      should eq #<Context id: 2, type: nil> (FAILED - 1)
  student built from a program
    program
      should eq #<Program id: 3, type: "Program">
  student built from a teacher through a program
    program
      should eq #<Program id: 4, type: "Program"> (FAILED - 2)

Failures:

  1) active record role built from a role through context context 
     Failure/Error: its(:context) { should eq(context) }
       
       expected: #<Context id: 2, type: nil>
            got: nil
       
       (compared using ==)
     # ./spec/build_has_many_through_association_spec.rb:63:in `block (3 levels) in <top (required)>'

  2) active record student built from a teacher through a program program 
     Failure/Error: its(:program) { should eq(program) }
       
       expected: #<Program id: 4, type: "Program">
            got: nil
       
       (compared using ==)
     # ./spec/build_has_many_through_association_spec.rb:75:in `block (3 levels) in <top (required)>'

Finished in 0.23493 seconds
4 examples, 2 failures

Failed examples:

rspec ./spec/build_has_many_through_association_spec.rb:63 # active record role built from a role through context context 
rspec ./spec/build_has_many_through_association_spec.rb:75 # active record student built from a teacher through a program program 

test_case_spec.rb

require 'bundler'
Bundler.setup

require 'active_record'

class Migrate < ActiveRecord::Migration
  self.verbose = false

  def up
    create_table :contexts do |t| t.string :type; end
    create_table :roles    do |t| t.string :type; t.references :context; end
  end
end

class Context < ActiveRecord::Base
  has_many :roles, :inverse_of => :context
end

class Role < ActiveRecord::Base
  belongs_to :context, :inverse_of => :roles
  has_many :roles, :through => :context
end

class Program < Context
  has_many :teachers, :foreign_key => "context_id", :inverse_of => :program
  has_many :students, :foreign_key => "context_id", :inverse_of => :program
end

class Teacher < Role
  belongs_to :program, :foreign_key => "context_id", :inverse_of => :teachers
  has_many :students, :through => :program
end

class Student < Role
  belongs_to :program, :foreign_key => "context_id", :inverse_of => :students
  has_many :teachers, :through => :program
end

describe "active record" do
  before(:all) do
    ActiveRecord::Base.establish_connection(:adapter => "sqlite3", :database => "db")
    Migrate.new.up
  end

  after(:all) do
    File.unlink("db")
  end

  let(:context) { Context.create }
  let(:role) { context.roles.create }
  let(:program) { Program.create }
  let(:teacher) { program.teacher.create }

  describe "role built from a context" do
    subject { context.roles.build }

    its(:context) { should eq(context) }
  end

  describe "role built from a role through context" do
    subject { role.roles.build }

    its(:context) { should eq(context) }
  end

  context "student built from a program" do
    subject { program.students.build }

    its(:program) { should eq(program) }
  end

  context "student built from a teacher through a program" do
    subject { teacher.students.build }

    its(:program) { should eq(program) }
  end
end