Pattern how to test a controller that needs a logged-in user in phoenix. Follows the example code written in https://pragprog.com/book/phoenix/programming-phoenix

example_controller_test.exs

defmodule N3ws.ChannelControllerTest do
  import Plug.Conn, only: [assign: 3]

  @valid_attrs %{name: "some content"}
  @invalid_attrs %{}
  @user_attrs %{
    email: "some content",
    name: "some content",
    password_virtual: "some content"
  }

  setup do
    user = Repo.insert!(User.registration_changeset(%User{}, @user_attrs))
    conn = assign(conn(), :current_user, user)
    {:ok, conn: conn}
  end

  test "creates resource and redirects when data is valid", %{conn: conn} do
    attrs = %{@valid_attrs | user_id: conn.assigns.current_user.id}
    conn = post conn, channel_path(conn, :create), channel: attrs
    assert redirected_to(conn) == channel_path(conn, :index)
    assert Repo.get_by(Channel, attrs)
  end

end