Delorean

Delorean lets you travel in time with Ruby by mocking Time.now

Marty:: Wait a minute, Doc. Ah... Are you telling me that you built a time machine... out of a DeLorean?

Doc:: The way I see it, if you're gonna build a time machine into a car, why not do it with some style?

Install

$ [sudo] gem install delorean

Or add it to your Gemfile, etc.

Usage

Let's travel in time!

require 'delorean'

# Date.today => Wed Feb 24
Delorean.time_travel_to "1 month ago" # Date.today => Sun Jan 24
Delorean.back_to_the_present          # Date.today => Wed Feb 24

With a block:

Delorean.time_travel_to("1 month ago") do
  # Inside the block, Time.now => Sun Jan 24 00:34:32 +0100 2010
  sleep(5)
  # And the time still goes by... Time.now => Sun Jan 24 00:34:37 +0100 2010
end

# Outside the block, Time.now => Wed Feb 24 00:34:35 +0100 2010

You can also jump which is like sleep but without losing time

# Time.now => Wed Feb 24 00:34:04 +0100 2010
Delorean.jump 30
# Time.now => Wed Feb 24 00:34:34 +0100 2010

Testing

Time-travelling can be extremely useful when you're testing your application.

For example, in RSpec you may find convenient to include Delorean's DSL in your spec_helper.rb:

RSpec.configure do |config|
  config.include Delorean
  ...

Now you can time-travel in your examples, like this:

it "should show latest created user" do

  time_travel_to(3.minutes.ago) { create_user :name => "John"  }
  time_travel_to(5.minutes.ago) { create_user :name => "Chris" }

  get 'show'

  response.should have_text("John")
  response.should_not have_text("Chris")

end

Don't forget to go back to the present after each example:

after(:each) { back_to_the_present }

or its alternate syntax:

after(:each) { back_to_1985 }

Credits

Delorean image based on an original by Giancarlo Pitocco.

Copyright (c) 2012 Luismi Cavallé, Sergio Gil and BeBanjo S.L. released under the MIT license