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Pivotal is proud to announce the release of the databasedotcom gem. Developed in partnership with Heroku and Salesforce, this gem wraps the Force.com REST API in familiar Ruby idioms, making it a snap to create web applications that integrate with your existing Salesforce instance, or even straight Ruby apps that do offline analysis of your Salesforce data.

I will be giving a session at Dreamforce on Tuesday, August 30, introducing the gem and demonstrating how easy it is to integrate into a Rails application. The session is entitled Building and Deploying Great Applications with Salesforce, Ruby, and Heroku, and takes place in Moscone West Room 2008 from 5:00 pm - 6:00 pm.

Source code from the session will be available soon, as will the session slides.

Hope to see you there!

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The Ugly Truth

On a recent project, we had an ActiveRecord model that declared some relationships and callbacks like so:

belongs_to :credit_card
before_create :build_credit_card

The intent was that build_credit_card would build the associated CreditCard instance, and ActiveRecord's default :autosave feature on the belongs_to would save it.

What we discovered was that no CreditCard object was being persisted. We confirmed that :autosave is on by default for belongs_to relationships, so we couldn't immediately understand why the new CreditCard wasn't being created.

Googling proved futile, so we dove right in to the ActiveRecord source- and boy did we have a good laugh about 10 minutes later.

What we found was that the :autosave option works by simply declaring a before_save callback- that makes perfect sense.

In our case, however, we were building the object to be autosaved in a before_create callback, which ActiveRecords runs after the before_save callbacks (cf. the callback ordering docs).

So our first problem was that we needed to move the call to build_credit_card from a before_create callback to a before_save :on => :create callback.

Did you catch that? There is a difference between before_create and before_save :on => :create. A big difference.

While I understand the how and why of this, the semantics don't make it obvious. So beware!

Now with our declarations changed to

belongs_to :credit_card
before_save :build_credit_card, :on => :create

We ran our tests again, and, still, no love. Ahhh, we've still got an ordering problem. In addition to the ordering semantics detailed in the docs, ActiveRecord also runs callbacks within a single group in the order in which they are declared. So, even though we changed the call to build_credit_card to occur in a before_save, it was still occurring after the :autosave before_save callback, because of the declaration order.

Finally, we changed our declarations to

before_save :build_credit_card, :on => :create
belongs_to :credit_card

and our tests were happy.

Takeaways

• When using autosave with any ActiveRecord association, be very careful of callback ordering if you are building or modifying the inverse objects using ActiveRecord callbacks.

• before_create isn't ever the same thing as before_save :on => :create, even if it sounds like it should be.

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Update

Since this article was written, version 1.7.0 of WebMock has been released, which includes WebMock.disable! functionality, as well as fixes the problem with selenium-webdriver. So please use that, instead of webmock-disabler.

The Problem

Recently, one of my projects ran into a problem where our integration tests would intermittently fail with weird timeout errors and complaints about page elements that couldn't be found.

A little googling revealed that we weren't the only ones having this problem.

Apparently, WebMock, Selenium, and WebDriver don't play nicely together, even if you tell WebMock to allow the outgoing connections necessary to drive the browser.

Some Gemfile hacking revealed that it was the mere presence of WebMock that caused the error. If we removed WebMock from our Gemfile, our integration tests ran fine, but then of course all of our tests that actually needed WebMock failed.

At that point, we could have decided to run our integration tests separately from the rest of the tests, but we really liked the idea of having all the tests run in the same VM, to avoid the duplicate VM startup time.

What we really needed was a way to turn WebMock on and off selectively for different types of tests.

The Solution

With some gnarly monkey patching and offensive use of alias_method, I have created webmock-disabler, a gem which provides new WebMock.disable! and WebMock.enable! methods. You can use these methods in individual tests, or on classes of tests as shown in the README.

The Result

We're now able to run our tests that need WebMock in the same VM as those that would otherwise break if we didn't do WebMock.disable!.

Celebration time!

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Interesting

RSpec 2.5, Capybara, and Selenium

Capybara, Selenium, and RSpec's request specs play nicely together, and you can even run tests that require javascript, using the :js => true option.

However, doing do requires the very latest Capybara, so be sure to specify the :git option in your Gemfile.

Ryan Bates has done an excellent RailsCasts episode on just this.

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