Mocking out time

If you want to fake out time in a Ruby test, there are three things to think about:

1. Editing the actual system time will prevent you from running tests in parallel, will break HTTPS/SSL certificate authentication, and will generally wreak havoc on most modern computers

2. Editing the value of when "now" is for Time and Date in Ruby means that your Ruby code will have a very different time than your database, any network dependencies, and any binaries you shell out to

3. Freezing time to a specific, fixed value can open the door to bugs due to code that comes to depend on that fixedness. For example, two measurements of "now" equalling one another when that can never be guaranteed to happen in production

Where does that leave you? I don't know, but Mocktail doesn't do anything to help you here.

The best tool for this job is definitely the timecop gem. Just use its travel methods to shift the Ruby-time to where you want, and be mindful that the time will disagree with any network or system dependencies.

Oh, and if you're looking at the ActiveSupport time helpers, just know that even when they say travel, they're actually freezing time, which creates the category of problems described in issue #3 above.

If you've heard enough, you can go back and consider non-TDD use cases for Mocktail.

Or if you're finally ready to walk the golden path, you can revisit Mocktail as a TDD tool.