First Phoenix API test

subscriber_controller_test.exs

defmodule Quotes.SubscriberControllerTest do
  use Quotes.ConnCase
  import Quotes.Factory

  test "#index renders a list of subscribers" do
    conn = build_conn()
    subscriber = insert(:subscriber)

    conn = get conn, subscriber_path(conn, :index)

    assert json_response(conn, 200) == %{
      "subscribers" => [%{
        "first_name" => subscriber.first_name,
        "last_name" => subscriber.last_name,
        "inserted_at" => DateTime.to_iso8601(subscriber.inserted_at), # Same error if I use Ecto.DateTime here
        "updated_at" => subscriber.updated_at
      }]
    }
  end
  
  describe "#create" do
    test "renders the created subscriber" do
      conn = build_conn()
      subscriber = %{
        first_name: "Harry",
        last_name: "Potter"
      }

      conn = post conn, subscriber_path(conn, :create, subscriber: subscriber)

      assert json_response(conn, 201) == %{
        "subscriber" => %{
          "first_name" => subscriber.first_name,
          "last_name" => subscriber.last_name
        }
      }
    end
  end
end

test_output.txt

mix test
...

  1) test #index renders a list of subscribers (Quotes.SubscriberControllerTest)
     test/controllers/subscriber_controller_test.exs:5
     ** (FunctionClauseError) no function clause matching in DateTime.to_iso8601/1
     stacktrace:
       (elixir) lib/calendar.ex:1642: DateTime.to_iso8601(~N[2017-01-07 15:12:12.257267])
       test/controllers/subscriber_controller_test.exs:15: (test)

.

Finished in 0.1 seconds
5 tests, 1 failure

Randomized with seed 182402