Setting invalid JSON terminally breaks ActiveRecord object [Rails 4.2/PG using json datatype]

invalid_json_test.rb

unless File.exist?('Gemfile')
  File.write('Gemfile', <<-GEMFILE)
    source 'https://rubygems.org'
    gem 'rails', github: 'rails/rails'
    gem 'arel', github: 'rails/arel'
    gem 'pg'
  GEMFILE

  system 'bundle'
end

require 'bundler'
Bundler.setup(:default)

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

# Note that testing jsonb datatype in pg requires Postgres 9.4. This behavior exists with json as well as jsonb datatypes.
ActiveRecord::Base.establish_connection(adapter: 'postgresql', host: 'localhost', username: 'postgres', password: 'yourpwd', database: 'yourdb')
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :posts, force: true  do |t|
    t.json :content
  end
end

class Post < ActiveRecord::Base

end

class BugTest < ActiveSupport::TestCase
  def test_setting_invalid_json_terminally_breaks_activerecord_object
    post = Post.create!
    post.content = {title: 'This is a Hash'}
    assert_nothing_raised{post.save!}
    # Attempting to set content to invalid JSON raises an error
    assert_raises(JSON::ParserError) {post.content = 'foo'}
    # But after this error is raised, the object is terminally broken as we cannot reset the attribute
    post.content = {title: 'This is a Hash'}
    # I can buy that the invalid assignment would result in an error, but terminally breaking the object seems undesirable.
  end
end