Rails rollback does not revert to previous dirty state bug

rails_rollback_dirty_bug.rb

require 'bundler'
Bundler.setup(:default)

require 'active_record'
require 'minitest/autorun'
require 'logger'

# 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 :foos do |t|
    t.integer :n
  end

  create_table :bars do |t|
    t.integer :n
  end
end


class Foo < ApplicationRecord
end

class Bar < ApplicationRecord
  validates :n, presence: true, numericality: { greater_than_or_equal_to: 0 }
end


class BugTest < Minitest::Test
  def test_not_so_dirty
    foo = Foo.create(n:1)
    bar = Bar.create(n:1)

    begin
      Bar.transaction do
        foo.n = -1
        foo.save!
        bar.n= -1
        bar.save! # will trigger validation error
      end
    rescue ActiveRecord::RecordInvalid => invalid
    end


    assert_equal 1, foo.n_was
    assert_equal 1, bar.n_was

    assert_equal -1, foo.n
    assert_equal -1, bar.n
  end
end