How could I create factories for a cyclic association in FactoryGirl?

Question

I've been having trouble trying to create factories for some objects and associations that I have defined in my project. I have a cyclic kind of association, where an object is associates with two other objects that afterwards join together.

+--------------+           +-------------+
|              |           |             |
| TestCase     +---------> | TestDataGrid|
|              |           |             |
+------+-------+           +------+------+
       |                          |
       |                          |
       |                          |
       v                          v
+--------------+           +--------------+
|              |           |              |
|              |           |              |
| TestVariable |           | TestDataSet  |
|              |           |              |
+------+-------+           +------+-------+
       |                          |
       |                          |
       |                          |
       |                          |
       |     +---------------+    |
       |     |               |    |
       |     |               |    |
       +---> | TestDataValue |<---+
             |               |
             +---------------+

---

class TestCase < ActiveRecord::Base
  has_many :test_variables, dependent: :destroy
  has_many :test_data_grids
  #...omitted code...
end

class TestVariable < ActiveRecord::Base
  belongs_to :test_case
  has_many :test_data_values
  #...omitted code...
end

class TestDataValue < ActiveRecord::Base
  belongs_to :test_variable
  belongs_to :test_data_set
  #...omitted code...
end

class TestDataSet < ActiveRecord::Base
  belongs_to :test_data_grid
  has_many :test_data_values
  #...omitted code...
end

class TestDataGrid < ActiveRecord::Base
  belongs_to :test_case
  has_many :test_data_sets
  #...omitted code...
end

Basically the association splits in TestCase and is joined again in TestDataValue, how could I create a Factory that opens and closes the circle with the same objects?

Gingivitis

Do you really need that? In most of the cases you can mock and stub all that relations. It's extremely hard to maintain such complex factories. – Overtrade

Answer 1

This isn't tested, but:

FactoryGirl.define do

 factory :test_data_value do
  test_data_set
  test_variable
  # attributes
 end

 factory :test_data_set do
  test_data_grid
  # attributes
 end

 factory :test_variable do
  test_case
  # attributes
 end

 factory :test_case do
  # attributes
 end

 factory :test_data_grid do
  test_case
  # attributes
 end
end

Then in specs:

@test_data_value = FactoryGirl.create(:test_data_value)

@test_variable = @test_data_value.test_variable
@test_data_set = @test_data_value.test_data_set

Idolah

the problem with this would be that :test_variable and :test_data_grid would create different instances of a :test_case if I am not mistaken, and I really need this to be the same object. – Gingivitis

I had similar FactoryGirl questions about complex test setup. I solved it by calling ThoughtBot and buying an hour of their time. I know this is an unusual; I'm suggesting it here because a) it's worked for me, b) you're offering a large bounty so I'm guessing you want a top-quality answer soon, and c) you're asking a good solid question. – Botryoidal

Answer 2

My suggestion would be to not set it up in the factories but in the tests themselves.

Factory file (thanks to @veritas1)

FactoryGirl.define do

  factory :test_data_value do
    # attributes
  end

  factory :test_data_set do
    # attributes
  end

  factory :test_variable do
    # attributes
  end

  factory :test_case do
    # attributes
  end

  factory :test_data_grid do
    # attributes
  end
end

Test file

@test_case = FactoryGirl.create(:test_case)
@test_data_grid = FactoryGirl.create(:test_case)
@test_variable = FactoryGirl.create(:test_case)
@test_data_set = FactoryGirl.create(:test_case)
@test_data_value = FactoryGirl.create(:test_case)
@test_case.test_data_grids << @test_data_grid
@test_case.test_variables << @test_variable
@test_data_grid.test_data_set << @test_data_set
@test_variable.test_data_values << @test_data_value
@test_data_set.test_data_values << @test_data_value

I know it might suck a little, but it sounds like the way to do it. As a thought though, if you're struggling with your tests it is usually a sign you'll struggle with it down the track and you should be redesigning the APIs. I can't see an alternative way of doing it, but you might be able to with the knowledge of the domain.

Gewgaw

Thinking about it, you could just use callbacks. Declare the associations as @Idolah said, but then in the TestCase factory, use a after create callback to setup everything similar to how I described before. github.com/thoughtbot/factory_girl/blob/master/… – Gewgaw

Answer 3

You can do it manually:

test_case = FactoryGirl.build(:test_case)

test = FactoryGirl.build(:test_data_value,
  :test_variable => FactoryGirl.build(:test_variable,
     :test_case => test_case
  ),
  :test_data_set => FactoryGirl.build(:test_data_set,
    :test_data_grid => FactoryGirl.build(:test_data_grid,
       :test_case => test_case
    )
  )
)

test.test_variable.test_case == test.test_data_set.test_data_grid.test_case
# => true

Or write some helper factory:

FactoryGirl.define do
  factory :test_data_value do
    ignore do
      test_case nil
      test_data_grid nil
    end

    test_variable do
      build :test_variable,
        :test_case => test_case 
                      || test_data_grid.try(:test_case) 
                      || build(:test_case)
    end

    test_data_set do
      build :test_data_set, :test_data_grid => test_data_grid || (
        build :test_data_grid, :test_case => test_case || build(:test_case)
      )
    end
  end
end

Test case as common ancestor:

test = FactoryGirl.create :test_data_value, 
  :test_case => FactoryGirl.build(:test_case)

test.test_variable.test_case == test.test_data_set.test_data_grid.test_case
# => true

Test case as common ancestor and the same test_data_grid for each instance:

test_data_grid = FactoryGirl.build :test_data_grid, 
  :test_case => FactoryGirl.build(:test_case)

test = FactoryGirl.create :test_data_value, 
  :test_data_grid => test_data_grid

test.test_variable.test_case == test.test_data_set.test_data_grid.test_case
# => true

Zamudio