bug_test.rb

# frozen_string_literal: true

gem "bundler", "< 1.16"

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"

  git_source(:github) { |repo| "https://github.com/#{repo}.git" }

  gem "pg", "<1.0"
  #gem "rails", "5.1.4" # success!
  gem "rails", "5.2.0" # fails!
end

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

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

ActiveRecord::Base.establish_connection(
  adapter: "postgresql",
  database: "rails_test",
  username: "user",
  password: "",
  host: 'localhost'
)
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :payments, force: true do |t|
    t.money    :cash
  end
end

class Payment < ActiveRecord::Base
  validates :cash, numericality: true, unless: :new_record?
end


class BugTest < Minitest::Test
  def test_numeric_validation
    payment = Payment.create!(cash: 2.0)

    payment.reload

    assert payment.cash == 2.0
    assert payment.valid?
  end
end

Found a syntax error -
https://gist.github.com/axlekb/6dfbfa45dd5e6137cb172e9cb37f4909#file-bug_test-rb-L51
Should be Payment.create!(cash: 2.0)

test.rb:49: syntax error, unexpected ':', expecting ')'
    payment = Payment.create!(:cash: 2.0)