by May 08, 2015

We work on a lot of different projects and are constantly shifting between them. Whether we're starting an application from scratch or picking up a 3 year old maintenance project, having a robust and comprehensive test suite is essential for us to maintain our sanity and ensure that changes are less likely to break something.

Here are a few of the testing gems that we add to every project we work on. We find them extremely useful and think you will too.

Should Matchers

We've been including the shoulda-matchers gem since the beginning and it has become an essential tool in our test suite.

This gem makes it simple to ensure that your model validations are well defined, associations exist, controllers are doing what you think they're doing, and more. For example:

describe User, type: :model do
  context 'associations' do
    it { should belong_to(:organization) }

  context 'validations' do
    %w(first_name last_name email password phone).each do |a|
      it { should validate_presence_of(a.to_sym) }

State Machine RSpec

This one is a little specific as it only works with RSpec and the state_machine gem, but we almost always have a state machine somewhere in our applications. Golden hammer!

Simply put, the state_machine_rspec gem helps ensure that you have the proper states defined in your state machine, with conditions, as well as the transitions between states.


While it's true that code coverage does not ensure a well tested application, it is still a useful metric. The simplecov gem helps us understand where and when we've slacked off on testing in a nicely consumable HTML format.

SimpleCov coverage report

Additionally, by setting the minimum coverage percentage, you can have simplecov return a non-zero status if coverage falls below a set limit. This is great for continuous integration and gives you a heads up quickly that recently introduced code is probably not tested well enough.


For applications that are time-sensitive, like public transit applications, the timecop gem is a must-have. This gem allows you to freeze time, jump back to a specific point in time to begin execution, or accelerate the passage of time.

At times, we've encountered intermittent problems with time-sensitive tests (e.g., when we run our tests after 5pm and UTC has rolled over to the next day). This gem has allowed us to mitigate these issues and make our test suite more reliable. If you're dealing with time then give this a try.


Similar to our need for timecop, we added the zonebie gem to our testing toolbox this year after we encountered intermittent test failures in timezone-sensitive tests.

Now, at the beginning of our test suite, we set a random timezone. This helps us make a robust test suite when dealing with users in different timezones. If you do encounter a problem in a specific timezone for a test run, it's easy to rerun the tests in that timezone using the ZONEBIE_TZ env var that is output at the beginning of each run. For example:

[Zonebie] Setting timezone: ZONEBIE_TZ="Eastern Time (US & Canada)"

# Rerun tests in the same timezone
$ ZONEBIE_TZ="Eastern Time (US & Canada)" rspec spec

In an effort to make our own lives easier, we test like crazy. These gems have all proven themselves over time and our test suite would be sad without them.

Have any testing gems or nuggets of wisdom to share? Hit us up on twitter @velocitylabs, we love to hear about it!

Curtis Miller

Curtis Miller

Managing Partner

Startup junkie, Rubyist and gamer. Loves to brainstorm about new ideas.

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