Your mix.exs file probably contains the following lines:

  defp elixirc_paths(:test), do: ["lib", "test/support"]
  defp elixirc_paths(_), do: ["lib"]

so the "test/support" folder which contains your DataCase isn’t compiled in the default env for the notebook (which is :dev).

But I think there is currently no way to set the MIX_ENV before attaching to the notebook.

You could add:

  defp elixirc_paths(:dev), do: ["lib", "test/support"]

above elixirc_paths(_) to compile the test/support files also in :dev.

Hi - I am so sorry about not responding to this. I missed the reply entirely. I’m buried with another item that I just posted on, but will circle back to this when I have some breathing room. I loved the idea of embedding tests rather than iex examples in the docs.

Cheers

I usually have an easier time running my app first via iex -S mix with a short name and cookie. After that you can configure Livebook to connect to your newly spawned iex process/node, as described in this blog post:

Here’s a similar thread on it as well:

Once that’s set up, all of your application code (including your use myApp.DataCase) should be mostly usable from Livebook.

Funnily enough I ran into this issue again, and my previous answer was close, but what I ended up doing is something like this:

MIX_ENV=test iex --sname nezteb --cookie nezteb -S mix phx.server

The MIX_ENV=test part is what I was missing last time. Livebook itself doesn’t need to run in test mode as long as you are using “Attached node” mode and connecting to your local iex sessions which is running with MIX_ENV=test.

Connect to the node in Livebook and then try something like this:

ExUnit.start(autorun: false)

defmodule MyAppTest do
  # use ExUnit.Case, async: true
  use MyApp.DataCase # this should work fine

  test "it works" do
    # Example using ExMachina (within the DataCase)
    user = insert(:user)
    assert user.id == 1
  end
end

ExUnit.run()

Example evaluation:

screenshot_2024-04-22_at_05.14.59@2x1200×849 49.1 KB