ActiveRecord: unable to delete records with a `has_one, through:` relationship

has_one_bug.rb

require "bundler/inline"

gemfile(true) do
  source "https://rubygems.org"
  gem "activerecord", "5.0.0"
  gem "sqlite3"
end

require "active_record"
require "minitest/autorun"
require "logger"

# Ensure backward compatibility with Minitest 4
Minitest::Test = MiniTest::Unit::TestCase unless defined?(Minitest::Test)

# This connection will do for database-independent bug reports.
ActiveRecord::Base.establish_connection adapter: "sqlite3", database: ":memory:"
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :identities
  create_table :tips
  create_join_table :identities, :tips, table_name: :identity_tips

  # =============================
  # ===== My temporary fix ======
  # =============================
  # # Adding a primary_key allieviates the issue
  # create_table :identity_tips, id: :primary_key do |t|
  #   t.references :tip, index: true
  #   t.references :identity, index: true
  # end
end

class Identity < ActiveRecord::Base
  has_many :identity_tips
  has_many :tips, through: :identity_tips
end

class IdentityTip < ActiveRecord::Base
  belongs_to :identity
  belongs_to :tip
end

class Tip < ActiveRecord::Base
  has_one :identity_tip
  has_one :identity, through: :identity_tip
end

class BugTest < Minitest::Test
  def test_identity_is_deletable_through_tip
    tip = Tip.create!
    identity = Identity.create!
    tip.update(identity: identity)
    new_identity = Identity.create!

    # bad things happen
    tip.identity = new_identity

    assert_equal(new_identity, tip.identity)
  end
end