StreamData x ExMachina

factory.ex

defmodule AppTemplate.Factory do
  alias AppTemplate.{Repo}
  use ExMachina.Ecto, repo: Repo
  alias AppTemplate.Generators

  def user_factory do
    Generators.generate(:user)
  end
end

generators.ex

defmodule AppTemplate.Generators do
  @moduledoc """
  Holds generator functions to provide generative data for testing

  For generators offered by StreamData, check here:
  https://hexdocs.pm/stream_data
  """

  use ExUnitProperties

  alias AppTemplate.{
    User
  }

  def generator(:user) do
    gen all email <- generator(:email) do
      %User{
        email: email,
        password: Bcrypt.hash_pwd_salt("password")
      }
    end
  end

  def generator(:email) do
    gen all local <- string(:alphanumeric, min_length: 1),
            domain <- string(:alphanumeric, min_length: 1) do
      String.downcase(local <> to_string(System.unique_integer()) <> "@" <> domain)
    end
  end

  def generate(generator_name, attributes \\ []) do
    1 |> generate_list(generator_name, attributes) |> List.first()
  end

  def generate_list(count, generator_name, attributes \\ []) do
    generator_name
    |> apply_attrs_to_generator(attributes)
    |> Enum.take(count)
  end

  defp apply_attrs_to_generator(generator_name, attributes) do
    generator_name
    |> generator
    |> Stream.map(&struct(&1, attributes))
  end

  def generate_string(max_length) do
    length = Enum.random(1..max_length)

    length |> :crypto.strong_rand_bytes() |> Base.url_encode64() |> binary_part(0, length)
  end
end

users_test.exs

defmodule AppTemplate.Users.Test do
  use AppTemplate.DataCase, async: true
  alias AppTemplate.Users

  test "create" do
    {:ok, user} =
      Users.create_user(%{
        "email" => "joe@example.com",
        "new_password" => "hi",
        "new_password_confirmation" => "hi"
      })

    assert user.email == "joe@example.com"
  end

  test "get_user_by_email" do
    user = insert(:user)
    user_from_db = Users.get_user_by_email(user.email)

    assert user.email == user_from_db.email
  end

  test "get_user" do
    user = insert(:user)
    user_from_db = Users.get_user(user.id)

    assert user.email == user_from_db.email
  end
end