test: add tests for join mail confirmation

test/membership/join_request_submit_email_test.exs

@@ -0,0 +1,34 @@
+defmodule Mv.Membership.JoinRequestSubmitEmailTest do
+  @moduledoc """
+  Unit tests for join request confirmation email on submit (Subtask 2).
+
+  Asserts that submit_join_request triggers sending exactly one confirmation email
+  (to the request email, with confirm link). Uses Swoosh.Adapters.Test; no integration.
+  Sender is wired in implementation; test fails until then (TDD).
+  """
+  use Mv.DataCase, async: true
+
+  import Swoosh.TestAssertions
+
+  alias Mv.Membership
+
+  @valid_submit_attrs %{
+    email: "join#{System.unique_integer([:positive])}@example.com"
+  }
+
+  describe "submit_join_request/2 sends confirmation email" do
+    test "sends exactly one email to the request email with confirm link" do
+      token = "email-test-token-#{System.unique_integer([:positive])}"
+      attrs = Map.put(@valid_submit_attrs, :confirmation_token, token)
+      email = attrs.email
+
+      assert {:ok, _request} = Membership.submit_join_request(attrs, actor: nil)
+
+      assert_email_sent(fn email_sent ->
+        to_addresses = Enum.map(email_sent.to, &elem(&1, 1))
+        to_string(email) in to_addresses and
+          (email_sent.html_body =~ "/confirm_join/" or email_sent.text_body =~ "/confirm_join/")
+      end)
+    end
+  end
+end