Can't use event-triggered ReadyToTest

Dockerfile

FROM ros:galactic

COPY setup.sh .
COPY launch.test.py .

RUN . /opt/ros/$ROS_DISTRO/setup.sh && python3 -m launch_testing.launch_test launch.test.py

launch.test.py

import unittest
import pytest

from launch import LaunchDescription
from launch.actions import ExecuteProcess, RegisterEventHandler
from launch.event_handlers import OnProcessExit
from launch_testing.actions import ReadyToTest


@pytest.mark.launch_test
def generate_test_description():
    setup = ExecuteProcess(cmd=["setup.sh"], output="screen")

    return (
        LaunchDescription(
            [
                setup,
                RegisterEventHandler(
                    OnProcessExit(target_action=setup, on_exit=ReadyToTest())
                ),
            ]
        ),
        {"setup": setup},
    )


class TestTeachAndRepeat(unittest.TestCase):
    def test_relying_on_setup(self, launch_service, proc_output):
        print("Running the test!")

setup.sh

#!/usr/bin/env bash
echo "Doing complicated setup logic"
sleep 10
echo "I'm done!"