Set default values on TraceTestCase to avoid errors on >=8.2.0 pytest

[claraberendsen]

Description

In pytest >=8.2.0 the unittest logic has been reworked to work more like a Function/Class, (see pytest-dev/pytest/pull/12089). This has the side-effect that during the collection phase all test are instantiated and given that the init func of TraceTestCase includes required keyword arguments not being fulfilled in the collection phase it errors.

This is avoided by setting default values on the init definition so a TraceTestCase.__init__() run during collection phase won't error.

pytest changelog: https://docs.pytest.org/en/stable/changelog.html#pytest-8-2-0-2024-04-27

Another approach to solve this would be to set __test__=false at the start to prevent pytest from collecting and instantiating the test, however that would need __test__=true for all of the subclasses of TraceTestCase that are actual tests for them to continue working. This seemed more cumbersome than this solution.

Fixes regressions on resolute

Is this user-facing behavior change?

Partially, even though default values are set were they would error if not present, this was already the case for two out of the four default keywords implicitly. It won't fail now if those arguments are not set, as it would before for the ones that had no implicit default value.

ros2_tracing/tracetools_test/tracetools_test/case.py

Lines 80 to 82 in 757d1a9

	self._session_name_prefix = \
	session_name_prefix + ('__' + rmw_implementation if rmw_implementation else '')
	self._events_ros = events_ros + [TRACE_TEST_ID_TP_NAME]

Did you use Generative AI?

No

Additional Information

Reference build:

Build with fixes:

Note that both have failed for reasons different to this PR, but in the later one there are 61 less regressions.

[christophebedard]

Seems OK to me with green CI if this doesn't affect the actual tests in any way (i.e., the value of these constructor arguments).

[claraberendsen]

Pulls: #236
Gist: https://gist.githubusercontent.com/claraberendsen/685e45f6ed27e02cdfab5a0e3ba0e73a/raw/d757847a7f509b8f97fdfd8e42c0a3f72f1ce397/ros2.repos
BUILD args: --packages-above-and-dependencies tracetools_test
TEST args: --packages-above tracetools_test
ROS Distro: rolling
Job: ci_launcher
ci_launcher ran: https://ci.ros2.org/job/ci_launcher/18329

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