Factory Girl: How to set up a has_many/through association

Try something like this. You want to build a detail object and append it to the job's detail association. When you use after_create, the created job will be yielded to the block. So you can use FactoryGirl to create a detail object, and add it to that job's details directly.

factory :job do
  ...

  after_create do |job|
    job.details << FactoryGirl.create(:detail)
  end
end

I faced this issue today and I found a solution. Hope this helps someone.

FactoryGirl.define do
  factory :job do

    transient do
      details_count 5 # if details count is not given while creating job, 5 is taken as default count
    end

    factory :job_with_details do
      after(:create) do |job, evaluator|
        (0...evaluator.details_count).each do |i|
          job.details << FactoryGirl.create(:detail)
        end
      end
    end
  end  
end

This allows to create a job like this

create(:job_with_details) #job created with 5 detail objects
create(:job_with_details, details_count: 3) # job created with 3 detail objects