Looping sequences in Factory Girl.

[Vikrant Chaudhary]

Hi,

I've a model Country with an attribute "code", which can only contain 2 characters (intended for ISO 3166-1 alpha-2 code).

In test/factories/countries.rb, I have

FactoryGirl.define do

  factory :country do

    sequence(:code, 'AA')

  end

end

However, this allows only a maximum of 26*26=676 Country records, after which validation starts failing (I've dozens of models and pretty much every model has association with Country). So I was wondering, if is it possible to loop over sequences in factory_girl? Or does this also count as an anti-pattern like resetting? - http://robots.thoughtbot.com/post/10983530140/getting-sequential-a-look-into-a-factory-girl

I wanted something like

 

  sequence(:code, 'AA'..'ZZ')

I think that this is a very general problem, however I couldn't find any references to it on web, which leads me to suspect that maybe I'm doing it wrong?

[Vikrant Chaudhary]

Ok, so this is what I'm doing now to loop 

#lib/loop_sequence.rb

class LoopSequence

  def initialize start, finish

    @cursor = @start = start

    @finish = finish

  end

  

  def to_s

    @cursor

  end

  

  def next

    #'AAA' is < 'ZZ', so can't do @cursor.next > @finish

    @cursor = (@cursor.next == @finish.next ? @start : @cursor.next)

    self

  end

end

#test/factories/countries.rb

FactoryGirl.define do

  factory :country do

    sequence :code, LoopSequence.new('AA', 'ZZ')

  end

end

[Vikrant Chaudhary]

I've just realised that in my above post @cursor.next == @finish.next doesn't really make sense. Correcting.

#lib/loop_sequence.rb

class LoopSequence

  def initialize start, finish

    @cursor = @start = start

    @finish = finish

  end

  

  def to_s

    @cursor

  end

  

  def next

    @cursor = @cursor == @finish ? @start : @cursor.next

    self

  end

end

[Peter Vandenabeele]

Hi Vikrant,

I see you are still working on this issue?

I won't say my solution is optimal, but what I typically do for such a 

standard case of "countries" etc. that are stored in tables is to make

one "default" country that is used for most tests as the default, and

only vary the country when the test is really about the country

attribute.

So that could be (untested code, written from top of my head)

FactoryGirl.define do

  # your original code

  factory :country do

    sequence(:code, 'AA')

  end

  factory :belgium, :parent => :country do

    code 'BE' # do not consume a sequence

  end

end

FactoryGirl.define do

  factory :address do

    ...

    # do not use "associate" because build hits the db

    country {FactoryGirl.build(:belgium)} 

  end

  factory :address_in_france, :parent => :address do

    ...

    country {FactoryGirl.build(:country, :code => 'FR')} 

    city "Paris"

  end

end

With this approach, all "default" address factories will just reuse

Belgium as country (avoiding the sequence overflow). When I

need a dedicated test for another country, I would then do something like:

it "country_code from country.code for France" do

  address = FactoryGirl.build(:address_in_france)

  address.country_code.should == "FR"

end

Of course this does not really address your original question of

sequencing in a set of limited size. But it is how I avoid this issue

altogether.

HTH,

Peter

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Peter Vandenabeele
http://twitter.com/peter_v

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[Vikrant Chaudhary]

Thanks Peter.

So far, I've been doing somewhat exactly that.

So instead of 

country {FactoryGirl.build(:belgium)} 

I'd been writing

country { Country.first || FactoryGirl.create(:country) }

However, since I've come up with the code in the third post of this thread, it has been serving me well. Now it doesn't feel like hacky any more. :-)

[Peter Vandenabeele]

On Thu, Feb 23, 2012 at 11:03 AM, Vikrant Chaudhary <nas...@gmail.com> wrote:

Thanks Peter.

So far, I've been doing somewhat exactly that.

So instead of 

country {FactoryGirl.build(:belgium)} 

I'd been writing

country { Country.first || FactoryGirl.create(:country) }

A little off-topic as you do have a different cyclical LoopSequence

now, but a difference that I find relevant is that this code above

will touch the database every time (first trying to find a country

and second creating one if not present; which could be quite often

if the test framework correctly rolls back the transaction after every

test).

My proposed code explicitly does not touch the database

when there are no create/save steps in the test (which can

be avoided in most business logic tests, if one pays some

attention to it). I started to become sensitive to that, to try to

make my tests and factory designs less dependent on the

persistence layer.

Especially as you mentioned that a "country" will be present

in most factory objects you create, it could be relevant for

performance and for decoupling the tests from the

persistence layer in general ...

HTH,

Peter

[Vikrant Chaudhary]

Yup! I was aware of the more database hits but that was all that I'd been able to come up with. Its all solved now though with LoopSequence. I guess this sort of functionality should already be in core. Something like