A plug to allow concurrent, transactional acceptance tests with Ecto.Adapters.SQL.Sandbox.

Example

This plug should only be used during tests. First, set a flag to enable it in config/test.exs:

config :your_app, sql_sandbox: true

And use the flag to conditionally add the plug to lib/your_app/endpoint.ex:

if Application.compile_env(:your_app, :sql_sandbox) do
  plug Phoenix.Ecto.SQL.Sandbox
end

It's important that this is at the top of endpoint.ex, before any other plugs.

Then, within an acceptance test, checkout a sandboxed connection as before. Use metadata_for/2 helper to get the session metadata to that will allow access to the test's connection. In general lines, you would write this:

setup tags do
  pid = Ecto.Adapters.SQL.Sandbox.start_owner!(YourApp.Repo, shared: not tags[:async])
  on_exit(fn -> Ecto.Adapters.SQL.Sandbox.stop_owner(pid) end)
  metadata_header = Phoenix.Ecto.SQL.Sandbox.metadata_for(YourApp.Repo, pid)
  # pass the metadata to the acceptance test library
  :ok
end

You can follow the instructions for Wallaby here.

Acceptance tests with channels

To support channels, in addition the above, you need to make it so each channel is allowed within the sandbox. The first step is to access the relevant header metadata.

To do so, you must declare that you want to pass connection information to your socket. This is typically the user agent header, but it can be a custom x-header too:

socket "/path", Socket,
  websocket: [connect_info: [:user_agent, …]]

socket "/path", Socket,
  websocket: [connect_info: [:x_headers, …]]

Now use the c:Phoenix.Socket.connect/3 callback to access the header and store it in the socket:

# user_socket.ex
def connect(_params, socket, connect_info) do
  {:ok, assign(socket, :phoenix_ecto_sandbox, connect_info.user_agent)}
end

Or if you are using a custom header:

Enum.find_value(connect_info.x_headers, fn
  {"x-my-custom-header", val} -> val
  _ -> nil
end)

This stores the value on the socket, so it can be available to all of your channels for allowing the sandbox.

# room_channel.ex
def join("room:lobby", _payload, socket) do
  allow_ecto_sandbox(socket)
  {:ok, socket}
end

# This is a great function to extract to a helper module
defp allow_ecto_sandbox(socket) do
  Phoenix.Ecto.SQL.Sandbox.allow(
    socket.assigns.phoenix_ecto_sandbox,
    Ecto.Adapters.SQL.Sandbox
  )
end

allow/2 needs to be manually called once for each channel, at best directly at the start of c:Phoenix.Channel.join/3.

Acceptance tests with LiveViews

LiveViews can be supported in a similar fashion to channels. First declare the :user_agent (or a custom header) in your live socket configuration in endpoint.ex:

socket "/live", Phoenix.LiveView.Socket,
  websocket: [connect_info: [:user_agent, session: @session_options]]

Now you can use the on_mount/4 callback to check the header and assign the sandbox:

defmodule MyApp.LiveAcceptance do
  def on_mount(:default, _params, _session, socket) do
    %{assigns: %{phoenix_ecto_sandbox: metadata}} =
      assign_new(socket, :phoenix_ecto_sandbox, fn ->
        if connected?(socket), do: get_connect_info(socket, :user_agent)
      end)

    Phoenix.Ecto.SQL.Sandbox.allow(metadata, Ecto.Adapters.SQL.Sandbox)
  end
end

Now, in your web.ex file, you can invoke this callback for all of your LiveViews if the sandbox configuration, defined at the beginning of the documentation, is enabled:

def live_view do
  quote do
    use Phoenix.LiveView
    # ...

    if Application.compile_env(:your_app, :sql_sandbox) do
      on_mount MyApp.LiveAcceptance
    end

    # ...
  end
end

Concurrent end-to-end tests with external clients

Concurrent and transactional tests for external HTTP clients is supported, allowing for complete end-to-end tests. This is useful for cases such as JavaScript test suites for single page applications that exercise the Phoenix endpoint for end-to-end test setup and teardown. To enable this, you can expose a sandbox route on the Phoenix.Ecto.SQL.Sandbox plug by providing the :at, and :repo options. For example:

plug Phoenix.Ecto.SQL.Sandbox,
  at: "/sandbox",
  repo: MyApp.Repo,
  timeout: 15_000 # the default

This would expose a route at "/sandbox" for the given repo where external clients send POST requests to spawn a new sandbox session, and DELETE requests to stop an active sandbox session. By default, the external client is expected to pass up the "user-agent" header containing serialized sandbox metadata returned from the POST request, but this value may customized with the :header option.

Finally, make sure your repository mode is set either to :manual or {:shared, self()} before the external client starts. This is typically done by default in your test/test_helper.exs, but you may need to do it explicitly depending on your setup:

Ecto.Adapters.SQL.Sandbox.mode(MyApp.Repo, :manual)