Testing Scopes with Lambdas

How do you know that your scopes are correct? At work we had been plagued by mysterious multiple payments in one of our apps. It had been coded to prevent multiple payments yet some customers were somehow managing to do it. After a thorough investigation, I discovered that the problem simply came down to one of the scopes used in the code had been written incorrectly. Here it is:

scope :current, where('start_date <= ?', Date.today).where('end_date > ?', Date.today)

Do you see the problem? It is a scope that checks the object is current, that it has started but not yet ended. Unfortunately, this scope is missing a lambda.

scope :current, lambda { where('start_date <= ?', Date.today).where('end_date > ?', Date.today) }

Without the lambda, the scope is set to the date when the scope was first loaded so that Date.today remain static until the next deploy or when the production app is restarted. So it’ll work fine for a day and then it’ll start misbehaving. The lambda effectively defer the evaluation of the expression until it is needed. So each time you use Authorisation.current it’ll use the current date which is what you want.

So how do we avoid this mistake? Here’s the wrong way to test a scope that uses a lambda:

expired_auth = Authorisation.create(start_date: 4.days.ago, end_date: 2.days.ago)
current_auth = Authorisation.create(start_date: 2.days.ago, end_date: 2.days.from_now)

Authorisation.current.should include(current_auth)
Authorisation.current.should_not include(expired_auth)

This will pass the original non-lambda scope. It passes because it’s not really testing the dynamic nature of the scope provided by the lambda. For this I use the Timecop gem:

auth = Authorisation.create(start_date: 2.days.ago, end_date: 2.days.from_now) # or use a factory to give you a current auth
Authorisation.current.should include(auth)

Timecop.freeze(2.days) # fast forward by 2 days so that the current auth is now by definition no longer current
Authorisation.current.should_not include(auth)

Now this test fails with the non-lambda scope. When I change the scope to use lambda, the test now passes.


Test Business Behaviour, Don’t Rely on UI

I often see Cucumber features written like this:

Given I a have an account with email: "user@test.com" and password: "password"
When I go to the log in page
And I fill in "Email" with "user@test.com"
And I fill in "Password" with "password"
And I press "Log in"
Then I should see "Logged in successfully."
And I should not see "Log in"

It works and does the job but I feel that it isn’t enough. It’s fragile in several ways.
Continue reading “Test Business Behaviour, Don’t Rely on UI”

Faster Cucumbering With Pagination

When writing a cucumber feature that involves pagination, the easiest thing to do is to create the required number of objects to generate pagination.

Given 31 tasks exist  # pagination defaults to 30

The downside of course is speed. Creating a large number of complex objects can add a lot of extra wait time to your cucumber runs. In my case, although I only had a few scenarios that involved pagination, my per_page setting was 50 and the objects I was creating were complex. The end result was a extra couple of (unnecessary) minutes. It wasn’t too bad so I left myself a TODO to fix it one day and that day finally came. Continue reading “Faster Cucumbering With Pagination”

Javascript Testing with Cucumber, Capybara and env.js

Tim Riley was excited when he discoved capybara and wrote an excellent blog post about Javascript Testing with Cucumber and Capybara. I was excited too but it took until I was sitting in a hallway at railsconf recharging my laptop before I found the time to clone Tim’s demo app and give capybara a try. I was impressed! I ran the tests and Firefox opened up in the background, ran the test and closed almost in a blink of the eye. Wow, that was fast. So much faster than how I’ve previously tested my javascript with selenium and webrat. And no complicated setup or configuration. Continue reading “Javascript Testing with Cucumber, Capybara and env.js”

Pomodoro FTW!

Do you pomodoro? It seems to be all the rage. It’s simple but effective, and I highly recommend it.

The Pomodoro Technique is about focus and maintaining that focus. In a sentence, it is about focusing on a single task for 25 minutes straight, no interruptions. Can you do it? For a lot of people, it is pretty hard. Email, twitter, facebook, SMS, and IM all compete for your attention and distract you from your work. People also like to procrastinate. When faced with a difficult task, you’d much rather do something easy and fun. It is common to leave essays and reports to the last minute. Continue reading “Pomodoro FTW!”

Leave It In My In-Tray

When I first started working in “the enterprise” one of the first things I learnt was how to prioritise. I called it my in-tray method. It worked well but it isn’t something I advocate. In fact, if you find yourself using this method then it’s time to find another job!

The in-tray method worked like this: whenever someone came to give me new work I’d ask them to leave it in my in-tray. Then I would completely ignore it. I would only deal with it if they came back for it. Most of the time they didn’t. Using this technique I could easily figure out what were the real priorities and simply forget the rest.

Continue reading “Leave It In My In-Tray”

Pickle Tables

Following on from my original and followup articles on using Pickle with Cucumber, a brand new version of Pickle is now available. Version 0.2.0 now gives you the ability to use Pickle with Cucumber’s multiline step argument tables. This means you can now do the following with Pickle:

Given a company exists
And another company: "rubyflare" exists
And the following people exist:
  | name  | age | employed | company              |
  | Digby | 13  | false    | the first company    |
  | Ethyl | 27  | true     | company: "rubyflare" |
Then the following people should exist:
  | name  | age |
  | Digby | 13  |
  | Ethyl | 27  |
And the 2nd person should be one of company: "rubyflare"'s employees

You can quickly create multiple objects in an easy to read fashion rather than filling your scenarios with multiple lines of “an another user exists …”. As an added bonus you can also use Pickle references within these tables. In the example above, we are creating new people objects and associating them to the companies using the Pickle references for these company objects.

Again, I’ll just point out that the above example required no custom step definitions. I didn’t have to write any step definitions! Pickle takes care of the grunt work leaving you free to focus on your domain specific scenario steps.

Other recent improvements with Pickle include:

  • an email helper for mapping names to email addresses similar to paths
  • its own separate configuration file (pickle.rb) – pickle no longer adds code to features/support/env.rb

I’ve also updated my pickle_example project to the latest version and have added the above example scenario. Feel free to clone it and use it to explore the benefits of using Pickle.

More Pickle Action

In a previous blogpost I championed the benefits of using Pickle with Cucumber to speed up your BDD. Recently, I was able to contribute back to Pickle in a small way with the following two changes:

This means you can do things like this in your plain text cucumber steps:

Given a user exists with name: "Digby", bank_balance: -43.25

And if you need to, you can also be explicit with the positive sign:

And another user exists with name: "Miranda", bank_balance: +86.50

The extra step definitions allow you to do the following:

Then a user should not exist with name: "Maya"
And the first user should not be one of the last user's debtors
And the last user should not be the first user's creditor

These are the “not” versions of some of the existing default step definitions. I found that I was needing these in my Rails projects and thought they would be good to have in the standard Pickle. Ian White, the creator of Pickle, agreed.

It feels good to contribute back to an open source project, even in a small way, and I encourage you all to try to do so as well.