hypothesis_test.py

# Standard library
import unittest

# Hypothesis and interfaces
from hypothesis import given, settings
from hypothesis.strategies import DrawFn, characters, composite, text
from std_msgs.msg import String

# Testing
from ros2_easy_test import ROS2TestEnvironment, with_single_node

# Module under test
from ..example_nodes.well_behaved import EchoNode


@composite
def ros2_preserved_string(draw: DrawFn) -> str:
    """We need to exclude NULL characters, because they are not preserved by ROS2."""
    return draw(
        text(
            alphabet=characters(
                blacklist_categories=[
                    "Cs",
                ],
                min_codepoint=1,
            )
        )
    )


@with_single_node(EchoNode, watch_topics={"/mouth": String})
@given(some_message=ros2_preserved_string())
@settings(max_examples=10, deadline=None)  # Remember that these tests are costly
def test_on_same_node(some_message: str, env: ROS2TestEnvironment) -> None:
    """This creates a single node and tests it with Hypothesis against many values.

    Note:
        You'll want to turn of the deadline, because these tests are costly.
    """

    env.publish("/ear", String(data=some_message))
    response: str = env.assert_message_published("/mouth").data
    assert response == some_message, (response, some_message)


@given(some_message=ros2_preserved_string())
@settings(max_examples=10, deadline=None)  # Remember that these tests are costly
@with_single_node(EchoNode, watch_topics={"/mouth": String})
def test_on_new_node_each(*, env: ROS2TestEnvironment, some_message: str) -> None:
    """This creates a single node and tests it with Hypothesis against many values.

    Note:
        This also switches the order of the arguments.
        To make that work, we need to use the ``*`` in the function signature
        to make ``env`` and ``some_message`` keyword-only arguments.
    """

    env.publish("/ear", String(data=some_message))
    response: str = env.assert_message_published("/mouth").data
    assert response == some_message, (response, some_message)


if __name__ == "__main__":
    unittest.main()