Taking your cucumber tests back to the future with Delorean

I’m currently working on an API for Vquence’s VQdata product which allows our customers to use a REST interface to retrieve videos with certain keywords they have previously stored. While writing tests I need to be able to mock out the Time object so that my tests were deterministic relative to time.

I remembered listening to a Ruby5 podcast which mentioned a great little gem called Delorean.

Delorean easily allows you to mock time in your tests. In no time I had hooked it up to cucumber.

In features/support/delorean.rb:

require 'delorean'  
                    
# Make sure we fix the time up after each scenario
After do
  Delorean.back_to_the_present
end

and then in features/step_definitions/delorean_steps.rb

Given /^I time travel to (.+)$/ do |period|
  Delorean.time_travel_to(period)
end      

this lets me create steps like

  Scenario: Link attributes are correct for yesterday
    Given I time travel to 2010-02-01 05:00
    When I GET the videos keywords feeds page
    Then I should see "start_time=2010-02-01T00:00:00"

Some other examples you can use with Delorean are

• 2 weeks ago
• tomorrow
• next tuesday 5pm

You can find more examples in the Chronic gem documentation which Delorean uses to achieve this functionality.