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https://github.com/batate/blacksmith

Data generation framework for Elixir
https://github.com/batate/blacksmith

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Data generation framework for Elixir

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Blacksmith

==========



Data generation framework for Elixir.



In testing, sometimes it's useful to create records in the form of maps. Blacksmith makes it easy.



First, install Blacksmith:



In your mix.exs file, add the blacksmith dependency:



~~~elixir

def deps do

  [{:blacksmith, "~> 0.1"}]

end

~~~



You will also have to add `:blacksmith` to your application list:



~~~elixir

def application do

  [applications: applications(Mix.env)]

end



defp applications(:test), do: applications(:all) ++ [:blacksmith]

defp applications(_all),  do: [:logger]

~~~



Next, tell Blacksmith how to save one record, or many records:



~~~elixir

defmodule Blacksmith.Config do

  def save(model) do

    MyRepo |> save(model)

  end



  def save_all(list_of_models) do

    MyRepo |> save_all(list_of_models)

  end

end

~~~



Next, perhaps in test_helper for convenience or somewhere in lib for speed, register each of your new models with Forge. Use [Faker](https://github.com/igas/faker) for fake values, and sequences to maintain unique values:



~~~elixir

defmodule Forge do

  use Blacksmith

  register :user,

    name: Faker.Name.first_name,

    email: Sequence.next(:email, &"test#{&1}@example.com"),

    description: Faker.Lorem.sentence,

    roles: [],

    always_the_same: "string"



  # this will create a user with roles set to [:admin]

  register :admin,

    [prototype: :user],

    roles: ["admin"]

end

~~~



Now you can create a user, generating all of the default values:



~~~elixir

  user = Forge.user

~~~



or a saved user, with the name attribute overridden, and a new attribute of favorite_language:



~~~elixir

  user = Forge.saved_user

           name: "Will Override",

           favorite_language: "Elixir"

~~~



or a list of 5 users



~~~elixir

  user = Forge.user_list 5

~~~



or a saved list of 5 admins



~~~elixir

  admin = Forge.saved_admin_list repo, 5

~~~



Create a list using a few common data elements:



~~~elixir

  Forge.having survey_id: some_survey.id, author: Forge.user do

    question = Forge.question   # will share the same survey id and user from above

  end

~~~



Next release: allow nesting of having blocks.



## Using with Ecto



Blacksmith can be used easily with a database persistence library such as Ecto.



~~~elixir

defmodule User do

  use Ecto.Model



  schema "users" do

    field :name, :string

    field :email, :string

  end

end

~~~



The `@save_one_function` and `@save_all_function` attributes are used to delegate to your persistence layer. We delegate to `Blacksmith.Config` defined below. You'll also notice that we directly create a struct in `register :user`, that's because Ecto works with models built on structs instead of plain maps.



~~~elixir

defmodule Forge do

  use Blacksmith



  @save_one_function &Blacksmith.Config.save/1

  @save_all_function &Blacksmith.Config.save_all/1



  register :user, %User{

    name: "John Henry",

    email: Sequence.next(:email, &"jh#{&1}@example.com")

  }

end

~~~



`Blacksmith.Config` defines the callback functions that delegate to the Ecto repository for persistence.



~~~elixir

defmodule Blacksmith.Config do

  def save(map) do

    MyRepo.insert(map)

  end



  def save_all(list) do

    Enum.map(list, &MyRepo.insert/1)

  end

end

~~~



`Forge.saved_user` will generate a `User` model that have been inserted in the database backed by `MyRepo`.