An app's tests of its mailboxes and routes.

import Letterbox.Test

test "photographs sent to a site are in its library", %{site: site} do
  inbound =
    deliver(
      from: "ana@example.com",
      to: "site+#{site.inbound_token}@in.example.com",
      subject: "From the beach",
      attachments: [%{name: "praia.jpg", content_type: "image/jpeg", data: File.read!("test/fixtures/praia.jpg")}]
    )

  assert inbound.status == "delivered"
  assert [%{name: "praia.jpg"}] = Media.list(site)
end

deliver/2 goes the whole way, as a webhook's message would: kept (in the app's store, Storehouse.Memory in tests), a row in the app's database (Ecto's sandbox), and given to its mailbox in the test's own process, at once. message/2 makes a Letterbox.Message only, to call a mailbox's process/1 with it; mailbox_for/2 says which mailbox takes one.