Recursively defining fixtures

fixtures.ex

defmodule Fixtures do
  def user do
    quote do
      def user, do: :user
    end
  end

  def client do
    quote do
      # You can use fixtures recursively.
      use Fixtures, [:user]

      def client, do: user()
    end
  end

  def apply_fixture(fixture) do
    quote do
      # Import the fixture only if it has not been imported previously.
      unless unquote(fixture) in Module.get_attribute(__MODULE__, :fixtures) do
        # Register the fixture import
        Module.put_attribute(__MODULE__, :fixtures, unquote(fixture))

        unquote(apply(__MODULE__, fixture, []))
      end
    end
  end

  defmacro __using__(fixtures) when is_list(fixtures) do
    attribute_registration =
      quote do
        Module.register_attribute(__MODULE__, :fixtures, accumulate: true)
      end

    fixtures =
      for fixture <- fixtures, is_atom(fixture), do: apply_fixture(fixture)

    [attribute_registration | fixtures]
  end
end