https://github.com/rails/rails/issues/10485

bug.rb

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 :posts do |t|
    t.string :title
  end
end

class Post < ActiveRecord::Base
end

class BugTest < MiniTest::Unit::TestCase
  def test_stuff
    post = Post.new(title: 12345)
    post.save!
    assert_equal "12345", post.title
  end
end