How do I set an _id value in FactoryBot that isn't a foreign key?

Question

I'm using FactoryBot (formerly FactoryGirl) to create some factory data for my tests. I have a model that looks like this via the schema (stripped down to just the relevant stuff):

create_table "items", force: :cascade do |t|
    t.text "team"
    t.text "feature_id"
    t.text "feature"
    t.timestamps
end

However, feature_id and feature are NOT references to a feature object... they are just strings.

I've defined my factory like this:

FactoryBot.define do
  factory :item do
    team "TheTeam"
    sequence(:feature_id) {|n| "Feature#{n}" }
    feature { Faker::Lorem.sentence }
  end
end

And the simple case works:

> FactoryBot.create(:item)
=> #<Item:0x007fad8cbfc048
 id: 1,
 team: "TheTeam",
 feature_id: "Feature1",
 feature: "Qui voluptatem animi et rerum et.",
 created_at: Wed, 10 Jan 2018 02:40:01 UTC +00:00,
 updated_at: Wed, 10 Jan 2018 02:40:01 UTC +00:00>

But when I want to specify my own feature_id this is what happens:

> FactoryBot.create(:item, feature_id: "123")
=> #<Item:0x007fad8d30a880
 id: 2,
 team: "TheTeam",
 feature_id: "123",
 feature: nil,
 created_at: Wed, 10 Jan 2018 02:40:59 UTC +00:00,
 updated_at: Wed, 10 Jan 2018 02:40:59 UTC +00:00>

You can see that feature is now nil. I'm assuming this is because it's trying to infer that feature_id and feature are somehow related. But in this case, I don't want them to be.

Is there a better way to define the factory so that it just treats them as unrelated fields?

BTW, if I try to set both the feature_id and feature it looks like this:

> FactoryBot.create(:item, feature_id: "123", feature: "hi")
=> #<Item:0x007fad8d262810
 id: 3,
 team: "TheTeam",
 feature_id: nil,
 feature: nil,
 created_at: Wed, 10 Jan 2018 02:45:01 UTC +00:00,
 updated_at: Wed, 10 Jan 2018 02:45:01 UTC +00:00>

So it just sets both fields to nil. I suspect FactoryBot is trying to be "smart" about these fields based on their names. I'd change them but they are already set that way in the Db.

Answer 1

It does appear that FactoryBot is making assumptions, and I haven't found a way to change those assumptions. It might be worth opening an issue to see what the maintainers have to offer.

In the mean time, here's a workaround:

FactoryBot.define do
  FEATURE_IDS ||= (1..1000).cycle

  factory :item do
    team "TheTeam"

    transient { without_feature_id false }
    transient { without_feature false }

    after(:build, :stub) do |item, evaluator|
      item.feature_id = "Feature#{FEATURE_IDS.next}" unless evaluator.without_feature_id
      item.feature = Faker::Lorem.sentence unless evaluator.without_feature
    end
  end
end

This will function properly in the cases you described above.

The incrementing is tricky. I was not able to find a way to use FactoryBot sequences outside of the resource-construction context, so I use an Enumerator and call #next to create the sequence. This works similar to a FactoryBot sequence, except that there is no way to reset to 1 in the middle of a test run.

RSpec tests prove it works as expected, whether we are creating items in the database or building them in memory:

context 'when more than one item is created' do
  let(:item_1) { create(:item) }
  let(:item_2) { create(:item) }

  it 'increments feature_id by 1' do
    expect(item_1.feature_id).to be_present
    expect(item_2.feature_id).to eq(item_1.feature_id.next)
  end
end

context 'when using build instead of create' do
  let(:item_1) { build(:item) }
  let(:item_2) { build(:item) }

  it 'increments feature_id by 1' do
    expect(item_1.feature_id).to be_present
    expect(item_2.feature_id).to eq(item_1.feature_id.next)
  end
end

Note that you cannot create an item without a feature_id or a feature using the typical construct; for example:

>> item = create(:item, feature_id: nil)

Will result in

>> item.feature_id
#> "Feature1"

If you wish to create an object without the feature and feature_id fields, you can do:

create(:item, without_feature_id: true, without_feature: true)