Create a custom test adapter.

README.md

@@ -52,6 +52,14 @@ The *hostname* option sets the FQDN to the header of your emails, its optional,
 
 4. Follow Bamboo [Getting Started Guide](https://github.com/thoughtbot/bamboo#getting-started)
 
+5. **Optional** Set `BambooSMTP.TestAdapter` as your test adapter:
+
+  ```elixir
+ # In your config/config.exs file
+ if Mix.env() == :test do
+   config :my_app, MyApp.Mailer, adapter: MyApp.SMTPTestAdapter
+ end
+ ```
 ## Usage
 
 You can find more information about advanced features in the [Wiki](https://github.com/fewlinesco/bamboo_smtp/wiki).

lib/bamboo/adapters/test_adapter.ex

@@ -0,0 +1,56 @@
+defmodule BambooSMTP.TestAdapter do
+  @moduledoc """
+  Based on `Bamboo.TestAdapter`, this module can be used for testing email delivery.
+
+  The `deliver/2` function will provide a response that follow the format of a SMTP server raw response.
+
+  No emails are sent, instead it sends back `{%Bamboo.Email{...}, {:ok,"<raw_smtp_response>"}}` 
+  for success and raise an exception on error.
+
+  ## Example config
+
+      # Typically done in config/test.exs
+      config :my_app, MyApp.Mailer,
+        adapter: BambooSMTP.TestAdapter
+
+      # Define a Mailer. Typically in lib/my_app/mailer.ex
+      defmodule MyApp.Mailer do
+        use Bamboo.Mailer, otp_app: :my_app
+      end
+  """
+
+  @behaviour Bamboo.Adapter
+
+  @doc false
+  def deliver(_email, _config) do
+    send(test_process(), {:ok, "Ok #{Enum.random(100_000_000..999_999_999)}"})
+  end
+
+  defp test_process do
+    Application.get_env(:bamboo, :shared_test_process) || self()
+  end
+
+  def handle_config(config) do
+    case config[:deliver_later_strategy] do
+      nil ->
+        Map.put(config, :deliver_later_strategy, Bamboo.ImmediateDeliveryStrategy)
+
+      Bamboo.ImmediateDeliveryStrategy ->
+        config
+
+      _ ->
+        raise ArgumentError, """
+        BambooSMTP.TestAdapter requires that the deliver_later_strategy is
+        Bamboo.ImmediateDeliveryStrategy
+
+        Instead it got: #{inspect(config[:deliver_later_strategy])}
+
+        Please remove the deliver_later_strategy from your config options, or
+        set it to Bamboo.ImmediateDeliveryStrategy.
+        """
+    end
+  end
+
+  @doc false
+  def supports_attachments?, do: true
+end