Rails Testing with Factory Girl

http://www.hiringthing.com/2012/08/17/rails-testing-factory-girl.html

by eatenbyagrue • 14 years ago

38 35 14 years ago

s_kilk• 14 years ago

I'm coming to the later stages of implementing an MVP with Rails and for me, FactoryGirl and RSpec have been a godsend.

Yea, once your model gets more complex than a dozen or so objects, then something like this is awesome. I only with there was an equivalent in ASP.Net MVC which is the current bill payer. (Plant is the closest I've seen, but not quite as elegant, and I'm a little concerned over support).

edandersen• 14 years ago

How is this different to mocking frameworks like RhinoMocks or the new Microsoft.Fakes?

ThePherocity2• 14 years ago

You're creating an actual instance of that object preloaded with whatever you need rather than a mock of that item which implements a fake implementation. They're not really competing since Mocks are most useful when mocking an interface, and Factory Girl is best at creating a number of usable objects.

calgaryeng• 14 years ago

Old news!

indrekju• 14 years ago

I hate when people are using it in the unit tests. It just makes testing very convenient, so they start using it everywhere. In the end, the test suite gets very slow. Unit tests should not hit the database.

First example there: test_new_customer_defaults. Really, it needs 3 saved models to test this? FactoryGirl isn't solution here. It's just hiding the problem.

urbanautomaton3• 14 years ago

If I could upvote the parent any harder, it would hit orbit.

If you need a complex network of collaborators to test a method, the answer is not to obscure the creation of those collaborators, it's to refactor so that each object talks only to its immediate neighbours, and then stub the heck out of them. If it absolutely has to be something that acts like an ActiveModel, then use mock_model().

samd2• 14 years ago

And I'd upvote it to Mars. FactoryGirl is completely an anti-pattern, unless maybe you're doing acceptance testing, but you know even then I wouldn't want FactoryGirl in my codebase, people would be too damn tempted to use it everywhere.

jeremyjh2• 14 years ago

You can use the build method to instantiate the model without saving to the database. Very useful because you only need use create when you need persistence in your test - such as when testing a controller.

urbanautomaton3• 14 years ago

Remember to ensure that your build strategy is set on all associations if you want this to work, e.g.

  FactoryGirl.define do
    factory :user do
      association :account, :strategy => :build
    end
  end

Otherwise when you build a user, the account association will still get persisted to the database.

Even if you do this, though, you're still spinning up a whole network of real objects in what is supposed to be a unit test.

j_s2• 14 years ago

One compromise (edit: on the performance problem) would be to use FactoryGirl to generate some type of (yaml?) cache pre-test-run, automatically refreshing only when the model changes.

davidcuddeback5• 14 years ago

I think you're missing the point of what makes FactoryGirl an anti-pattern in unit tests. FactoryGirl reduces the feedback that you can get from unit tests by hiding complexity (of creating objects), which your unit tests are supposed to make apparent.

Edited to add: Using FactoryGirl to generate a cache only addresses the performance issues without addressing the complexity-hiding problem.

gyardley• 14 years ago

Yep, I'm trying to dig myself out from this problem now.

The Rails Tutorial (railstutorial.org) uses Factory Girl and integration tests for just about everything, which is a fast enough approach for its toy application, but I've found that when your application gets more complex your test suite takes forever to run, and setting up the tests gets more and more painful (especially when you start dealing with external APIs).

Does anyone have any opinions on the best resource for teaching effective unit testing in Rails? I'd love to speed up my test suite while not losing coverage.

davidcuddeback5• 14 years ago

It's not really focused on unit testing (though it does cover it) so much as it's focused on good design, but the two are related, so I found Avdi's "Objects on Rails" [1] helpful.

[1] http://objectsonrails.com/

I'm not sure if it's the best resource, though. I'd love to hear other opinions.

briandear• 14 years ago

Factory Girl is good but Fabrication is far better.

sanderjd3• 14 years ago

A response from a naysayer:

Factories are slow. Yes, they really are. Persisting everything along a chain of associations will always be slower than properly isolating the dependencies of the unit under test, SSD or not. It's easier to enjoy Ruby when not constantly waiting minutes for tests to run.

Factories increase the over-all complexity of your app. Are you kidding me? Yes, they do. Expertise and huge, easy gains have nothing to do with reducing complexity and more often (but not always) increase it. A test suite where every test depends on state in a database is more complex than one that tests units in isolation.

None of these points are arguing against Factory Girl, which is a great tool for doing what it does; they are arguing against integrating with the database in "unit" tests.

darrencauthon• 14 years ago

As a guy who recently switched from years of ASP.Net MVC to Rails, I read this post and wanted to shout...

"Watch out everybody, he's hitting the database!!!"

Ruby is a great language that I love, but this is one of those cases where Ruby's conciseness and readability hide a TON of complexity. And complexity in tests is death.

I've seen it for myself -- there's a lot of technical debt interest in those tests. It looks manageable at the beginning, especially within the scope of a blog post, but when the app grows and grows and grows, the tests fail.

amurmann• 14 years ago

To get the best form both fixtures and factories, I can strongly recommend http://github.com/rdy/fixture_builder It utilizes factories to build up your fixtures. This way you only need to specify what you actually care about in you r fixture which preserves readability. But you still get the speed of fixtures. The one downside is that you can never assume a complete knowledge of what's in your DB. This might break test for scopes for example.

However I more and more agree with the general notion that your unit test should not hit the DB. However, Rails works against that. Avdi Grimm's "Object's on Rails" (http://objectsonrails.com/) has some interesting suggestions on how to get some good test isolation out of Rails.

rob-anderson• 14 years ago

Factory Girl has saved me countless hours - I love it.

You can use build instead of create to avoid the db, as per previous comments. You don't have to use it at all if writing a simple unit test.

But for teeing up complex scenarios prior to a fat integration test, it rocks.

Rails Testing with Factory Girl

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