Having a View, with a function using the Routes.*_url helper, everything works fine, until I try to test this function directly.

defmodule ExampleWeb.PageView do
  use ExampleWeb, :view

  def url_helper(conn, slug) do
    Routes.page_url(conn, :show, slug)
  end
end

defmodule ExampleWeb.PageViewTest do
  use ExampleWeb.ConnCase, async: true

  alias ExampleWeb.PageView

  test "url_helper/2", %{conn: conn} do
    slug = "my-example"

    assert PageView.url_helper(conn, slug) == "http://localhost:4002/my-example"
  end
end

Result when running the test:

1) test url_helper/2 (ExampleWeb.PageViewTest)
   test/example_web/views/page_view_test.exs:12
   ** (CaseClauseError) no case clause matching: %{phoenix_recycled: true, plug_skip_csrf_protection: true}
   code: assert PageView.url_helper(conn, slug) == "http://localhost:4000/my-example"
   stacktrace:
     (phoenix 1.5.3) lib/phoenix/router/helpers.ex:18: Phoenix.Router.Helpers.url/2
     (example 0.1.0) lib/example_web/router.ex:1: ExampleWeb.Router.Helpers.page_url/4
     test/example_web/views/page_view_test.exs:15: (test)

If I change this to use the Routes.*_path helper everything works as intended, but I need the complete and absolute urls form time to time.

Did I miss anything when setting up the conn for testing?