Refactory

An Elixir library to generate test data recursively with traits

Installation

The package can be installed by adding refactory to your list of dependencies in mix.exs:

def deps do
  [
    {:refactory, "~> 0.1.1", only: :test}
  ]
end

Documentation can found at https://hexdocs.pm/refactory/.

Refactory allows generating Ecto records with nested overrides for your tests.

Factory module

To start using Refactory, first define a factory module:

defmodule MyApp.Factory do
  use Refactory, repo: MyApp.Repo
end

Usage

The factory module has two functions:

• build/2 generates an Ecto record with the given traits applied
• create/2 inserts an Ecto record into the database

Traits

A trait can be

• a Map in which each key-value pair is either
  • a field with its value
  • an association with a trait (for belongs_to, has_one, and embeds_one)
  • soon: an association with a list of traits (for has_many and embeds_many)
• a custom trait defined in the factory module (see below)
• a Tuple with multiple traits to be applied

Basic example

defmodule MyApp.Factory do
  use Refactory, repo: MyApp.Repo
end

MyApp.Factory.build(MyApp.List, %{
  title: "Refined List",
  created_by_user: %{email: "test@email.org"}
})

%MyApp.List{
  title: "Refined List",
  created_by_user: %MyApp.User{
    email: "test@email.org"
  }
}

Default traits

Default traits can be defined in the factory module. They are always applied first.

defmodule MyApp.Factory do
  use Refactory, repo: MyApp.Repo

  def trait(MyApp.List, :default) do
    %{
      title: "Default Title"
    }
  end
end


MyApp.Factory.build(MyApp.List)

%MyApp.List{title: "Default Title"}

Custom traits

Custom traits can be defined in the factory module and then used by their name.

defmodule MyApp.Factory do
  use Refactory, repo: MyApp.Repo

  def trait(MyApp.List, :default) do
    %{
      title: "Default Title"
    }
  end

  def trait(MyApp.List, :with_admin_user) do
    %{
      created_by_user: %{
        role: :admin
      }
    }
  end
end


MyApp.Factory.build(MyApp.List, :with_admin_user)

%MyApp.List{title: "Default Title", created_by_user: %MyApp.User{role: :admin}}

Why another factory library?

To my knowledge, this is the only factory library that supports recursive traits, providing a powerful declarative appraoch to (test) data generation.

Recursive and/or nested approaches might be tricky in non-functional programming languages, because the resulting objects often encapsulate internal state. In Elixir, however, data structures are cleanly separated from behavior, making it a great field of application for recursive data structure generation.

Special thanks

This project is sponsored and kindly supported by Team Engine.

If you’d like to join us working on Dx and Refactory as a contractor, please reach out to @arnodirlam.