reproduce an rails issue

active_record_gem.rb

begin
  require 'bundler/inline'
rescue LoadError => e
  $stderr.puts 'Bundler version 1.10 or later is required. Please update your Bundler'
  raise e
end

gemfile(true) do
  source 'https://rubygems.org'
  # Activate the gem you are reporting the issue against.
  gem 'activerecord', '~> 5.0.7'
  gem 'activerecord-jdbcpostgresql-adapter'
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: 'postgresql', port: 5432,
                                        host: 'localhost',
                                        username: 'postgres', password: 'change_to_whatever_you_use')

ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :posts, force: true do |t|
    t.date :post_date
  end
end

class Post < ActiveRecord::Base
  validates_uniqueness_of :post_date
end

class BugTest < Minitest::Test

  def test_association_stuff
    post = Post.create!(post_date: Date.new(2001,1,1))
    assert post.valid?
  end

end