Update the RedirectionController.

test/link_shortener_web/controllers/redirection_controller_test.ex

@@ -0,0 +1,30 @@
+defmodule LinkShortenerWeb.RedirectionControllerTest do
+  use LinkShortenerWeb.ConnCase
+
+  import LinkShortener.LinksFixtures
+
+  alias LinkShortener.Links.Link
+  alias LinkShortener.Links
+
+  @invalid_shorten "invalid_shorten"
+
+  describe "redirection via a link" do
+    setup [:create_link]
+
+    test "redirected via the shorten", %{conn: conn, link: %Link{shorten: shorten} = link} do
+      conn = get(conn, ~p"/u/#{shorten}")
+      assert response(conn, 302)
+    end
+
+    test "no redirection if a shorten is not found", %{conn: conn, link: link} do
+      assert_error_sent 404, fn ->
+	conn = get(conn, ~p"/u/#{@invalid_shorten}")
+      end
+    end
+  end
+
+  defp create_link(_) do
+    link = link_fixture()
+    %{link: link}
+  end
+end