Elixir introduces into the world of programming, the "multiverse testing" pattern. This is a pattern where integration tests are run concurrently and each test sees a shard of global state.

pre-existing-examples

Pre-Existing Examples:

• Mox: each test has access to the global module mock, sharded by the pid of the running test.
• Ecto: each test has access to a "database sandbox", which is a checked out transaction on the global database that acts as its own database shard.
• Hound,Wallaby: each test generates an ID that is passed outside of the BEAM that is reintercepted on ingress, this ID is then used to connect ecto sandboxes to the parent test PID

This library implements Multiverses-aware versions of several constructs in the Elixir Standard Library that aren't natively Multiversable.

For plugins that are provided for other systems, see the libraries:

• :multiverses_http - which extends this to HTTP requests that exit the BEAM.
• :multiverses_pubsub - which extends this to Phoenix.PubSub

The following multiverse modules are provided by this core package:

• Multiverses.Application - which shards the application environment variables
• Multiverses.Registry - which shards Registries

usage

Usage

In mix.exs, add the following dependency:

{:multiverses, "~> 0.11.0", only: :test}

in-your-code

In your code

For example, if you would like to use the Multiverses version of the Application module (Multiverses.Application), add the following lines:

To config/config.exs:

config :my_app, Application, Application

To config/test.exs:

config :my_app, Application, Multiverses.Application

To the module where you would like to use multiverses Application:

@application Application.compile_env(:my_app, Application)

And where you would like to make a multiverses Application call:

def some_function do
  value = @application.get_env(:my_app, :some_env_variable)
  # ...
end

in-your-tests

In your tests

1. Register the module you'd like to substitute with multiverses.

setup do
  Multiverses.shard(Application)
end

2. Your tests have segregated application values!

defmodule MyModule do
  @application Multiverses.Application
  def get_and_wait(value) do
    @application.put_env(:my_app, :env, value)
    Process.sleep(1000)
    @application.get_env(:my_app, :env)
  end
end

defmodule SomeTest do
  use ExUnit.Case, async: true
  test do
    assert :foo == MyModule.get_and_wait(:foo)
  end
end

defmodule SomeOtherTest do
  use ExUnit.Case, async: true
  test do
    assert :bar == MyModule.get_and_wait(:bar)
  end
end