multiverses

defmodule MultiversesTest.Replicant do
  @moduledoc """
  allows you to replicate test module multiple times, forcing them to
  be run concurrently.  This helps prove that the system can be run
  in parallel without issue.

  you should set the replication level with the REPLICATION environment
  variable, for example:

  ```shell
  REPLICATION=10 mix test
  ```
  """

  @doc """
  use in place of `defmodule/2` for any test you'd like replicated.
  """
  defmacro defmoduler(module, do: do_block) do
    module = Macro.expand(module, __CALLER__)

    replication = "REPLICATION"
    |> System.get_env("1")
    |> String.to_integer

    for index <- 1..replication do
      module_instance = Module.concat(module, "Instance#{index}Test")
      quote do
        defmodule unquote(module_instance), do: unquote(do_block)
      end
    end
  end
end