---
title: Factory Bot 2.2, your new best friend!
teaser:
tags: news,web,open source,testing,rails,factory_girl,factory_bot
author: Josh Clayton
published_on: 2011-10-14
---

Aside from a handful of internal code clean up, [Factory Bot
2.2](http://rubygems.org/gems/factory_girl/versions/2.2.0) brings a handful of
awesomeness to the table. [Factory Bot 2.1 was released a mere month and a
half
ago](https://thoughtbot.com/blog/post/9713995255/factorybot-2-1-0-brings-the-heat)
but loads of improvements have been added since then. Some key features:

## Attributes from traits can be modified

When we introduced traits, there were a couple of caveats: you couldn't
override traits' attributes from child factories, and you couldn't overwrite
traits' attributes when using `FactoryBot.modify`. Not the case anymore!
We've been hammering away at Factory Bot's internals, cleaning things up and
delaying factory resolution as late as possible. This allows for:

    FactoryBot.define do
      factory :user do
        name { "Stranger" }

        trait :male do
          name { "Jon Snow" }
          gender { "Male" }
        end

        factory :male_user do
          male
        end

        factory :brandon do
          male
          name { "Brandon" }
        end
      end
    end

    FactoryBot.modify do
      factory :brandon do
        name { "Brandon Stark" }
      end
    end

## Parent factories can be defined after their children

This may sound a bit odd. Why would you ever want to define a parent factory
*after* a child factory? When you've split your factories up across different
files and don't want to prefix file names in order for the files to be loaded
in a specific order.

Factory Bot looks in six places by default: factories/, factories.rb,
spec/factories/, spec/factories.rb, test/factories/, and test/factories.rb. If
you've split up your factories within one of the directories, that's
wonderful; however, what if you want a "base" factory file and multiple
factory files for the various children? Before 2.2, you'd have to name that
base file in order to force it to be loaded before children, and that's just
gross.

## Transient attributes have a cleaner syntax

Transient attributes are a relatively new feature allowing attributes to be
passed via a hash when creating/building that don't actually interact with the
instance (or hash, when using `attributes_for`). The old syntax required
calling `#ignore` on individual attribute declarations, which didn't really
look great. Now, you define all your ignored attributes in a block.

    FactoryBot.define do
      factory :user do
        ignore do
          rockstar { true }
          four     { 2 + 2 }
        end

        name { "John Doe#{" - Rockstar" if rockstar}" }
      end
    end

The old ignore syntax has been deprecated and will be removed in 3.0.

## Factories now accept blocks and yield the result

Have you ever done this?

    let(:old_published_post) do
      create(:post, created_at: 2.years.ago).tap do |post|
        post.publish!
      end
    end

Now, you can just pass a block to the syntax methods (`create`, `build`,
`build_stubbed`, and `attributes_for`) and they'll yield themselves; no more
`tap`! It's a simple enough change, but four characters fewer is four
characters fewer.

## What's next for Factory Bot

Aside from getting in [solid pull
requests](https://github.com/thoughtbot/factory_bot/blob/master/CONTRIBUTING.md),
we're going to be reworking the test suite so it's much more flexible and
continue reworking the inner workings of the gem. There's currently a handful
of code surrounding how to evaluate attributes and the order in which we should
do so that we'd like to remove completely and have attributes resolve lazily.

We're also considering a new syntax method, `decorate`, which would allow for:

    FactoryBot.define do
      factory :post do
        title { "My great post!" }
        body { "An awesome story" }

        decorate :old do
          title { "How is this even around still?" }
          created_at { 2.years.ago }
        end

        decorate :archived do
          title { "This shouldn't be on the homepage" }
          archived { true }

          decorate :unpublished do
            published { false }
          end
        end
      end
    end

This would give us four factories: `post`, `old_post`, `archived_post`, and
`archived_unpublished_post`.

What features would you like to see in Factory Bot? Post them on [the GitHub
issues page](https://github.com/thoughtbot/factory_bot/issues) and let us
know in the comments!

* * *

**Disclaimer:**

Looking for FactoryGirl? The library was renamed in 2017.
[Project name history can be found here.](https://github.com/thoughtbot/factory_bot/blob/master/NAME.md)