assert_change 試作版

assert_change.rb

require 'test/unit/assertions'

module AssertChange
  # fixme message?
  def assert_change(value_proc, options = {}, &event_proc)

    change = Change.new(value_proc)
    change.perform(event_proc)

    case
    when options[:by]
      change.assert_change_by(options[:by])
    when options[:from], options[:to]
      change.assert_change_from_to(from: options[:from], to: options[:to])
    else
      change.assert_change
    end
  end

  def assert_not_change(value_proc, options = {}, &event_proc)
    change = Change.new(value_proc)
    change.perform(event_proc)
    change.assert_not_change
  end

  class Change
    include Test::Unit::Assertions

    attr_reader :actual_before, :actual_after

    def initialize(value_proc, message = nil)
      @value_proc = value_proc
      @message = message
    end

    def perform(event_proc)
      @actual_before = evaluate_value_block
      event_proc.call
      @actual_after = evaluate_value_block
    end

    def assert_change_by(by)
      assert { by == @actual_after - @actual_before }
    end

    def assert_change_from_to(from: nil, to: nil)
      assert_equal from, actual_before, "expect to change from #{from} but actual #{actual_before}" if from
      assert_equal to, actual_after, "expect to change to #{to} but actual #{actual_after}" if to
    end

    def assert_change
      assert_not_equal @actual_before, @actual_after, "expect to change #{@actual_before} but not change (actual: #{@actual_after})"
    end

    def assert_not_change
      assert_equal @actual_before, @actual_after, "expect not to change #{@actual_before} but changed (actual: #{@actual_after})"
    end

    private
    def evaluate_value_block
      val = @value_proc.call
      case val
      when IO
        val
      when Enumerable, String
        val.dup
      else
        val
      end
    end

  end

  private
end