[ROS2][foxy][launch testing] Integration testing with launch testing

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I would like to do integration test using https://index.ros.org/p/launch_testin.... I have based my self on the examples (https://github.com/ros2/launch/tree/m...) and I can launch the node and run unittest.TestCase but I am not sure how to check the output. All I can find is the launch_testing.asserts funcitons but it looks like I can only test exit codes and strings? I would like to test:

• a response from a service call
• a result from a published topic

Example of my code - currently I am only trying to test the response from the service: I can see that the node is launched and the service is called but I am not able to test the response

    import os
    import sys
    import unittest
    import launch.actions
    import launch.substitutions
    import lifecycle_msgs.msg
    import ament_index_python
    import launch_ros.actions
    import launch_ros.events
    import launch_ros.events.lifecycle
    import launch_testing
    import launch_testing.actions
    import pytest

    from launch import LaunchDescription
    from launch import LaunchService
    from launch.actions import ExecuteProcess
    from launch_ros.actions import Node
    from launch_testing.legacy import LaunchTestService                                                                                                           
    from my_srv_pkg.srv import MySrv
    from launch_testing.asserts import assertSequentialStdout

@pytest.mark.launch_test
    def generate_test_description():
        TEST_PROC_PATH = os.path.join(
            ament_index_python.get_package_prefix('launch_testing'),
            'lib/launch_testing',
            'my-pkg'
        )

        # This is necessary to get unbuffered output from the process under test
        proc_env = os.environ.copy()
        proc_env['PYTHONUNBUFFERED'] = '1'

        launch_node = launch.actions.ExecuteProcess(
            cmd=['ros2 launch my-pkg my_launch.py'],
            shell=True,
            env=proc_env, output='screen'
        )

    return launch.LaunchDescription([
        launch_node,
        launch_testing.actions.ReadyToTest()
    ])

class TestServiceCall(unittest.TestCase):
    def test_if_service_is_called(self, proc_output):
        call_service_action = ExecuteProcess(
        cmd=['ros2 service call /my_service my-pkg/srv/MySrv "{<request data>}"'],
        shell=True,
            name='call_service_action',
            output='screen')

            response = MySrv.Response()
            <populate response with expected value>

            # here I want to check the response - if it is the same to what I expect  
            proc_output.assertWaitFor(response, timeout=5)