adds let and it to ActiveSupport::TestCase

1-active-support-test-case-let-it.rb

class ActiveSupport::TestCase
  parallelize(workers: :number_of_processors)

  def self.let(name, &block)
    @@lets ||= SimpleHash.new
    @@lets[name] = block
  end

  def self.it(&block)
    name = "test_"
    name += self.class.name.underscore
    name += "_#{block.source.underscore}"

    define_method(name, &block)
  end

  def method_missing(name, *args, &block)
    super if args.any? || block
    super unless @@lets.has_key?(name)

    if @@lets.fetch(name).is_a?(Proc)
      @@lets[name] = @@lets.fetch(name).call
    end

    @@lets.fetch(name)
  end

  def respond_to_missing(name, include_private = false)
    @@lets.has_key?(name) || super
  end

  def methods
    super + @@lets.keys.map(&:to_sym)
  end
end

2-simple-hash-test.rb

require 'test_helper'

class SimpleHashTest < ActiveSupport::TestCase
  let(:data) { { a: 1, b: [{ c: { d: 2 } }, { e: 3 }], f: 4 } }

  it { assert_nothing_raised { SimpleHash.new(data) } }
  it { assert_nothing_raised { SimpleHash[data] } }
  it { assert_equal(SimpleHash[data].a, 1) }
  it { assert_equal(SimpleHash[data].b[0].c.d, 2) }
  it { assert_equal(SimpleHash[data].b[1].e, 3) }
  it { assert_equal(SimpleHash[data].f, 4) }
end