Move MockOptions into testutil library

[gshuflin]

The test for the v2 test goal defines a MockOptions type since it specifically needs to create an options mock. But this is really a more general piece of functionality that ought to live in a testutil library so other test files can make use of it.

[Eric-Arellano]

I'm not convinced that this is how we want to mock a GoalSubsystem. For example, we might want to leverage the prior art of init_subsystem. I think we should wait to see if we can come up with anything better.

[cosmicexplorer]

Great thinking!

[cosmicexplorer]

Suggested change

	"""Test mock for any options type."""
	"""Test mock for any `Optionable` subclass."""

[cosmicexplorer]

For example, we might want to leverage the prior art of init_subsystem.

I agree with this in theory, but it has also been super annoying to correctly use init_subsystem() for me personally in tests, so this approach seems quite nice to me. Perhaps a halfway point could be to validate that the options registered in MockOptions have been correctly registered?

[Eric-Arellano]

Ideally, a solution will fix this:

pants/src/python/pants/engine/goal_test.py

Lines 14 to 40 in e52a044

	@pytest.mark.skip(
	reason="Figure out how to create a GoalSubsystem for tests. We can't call global_instance()"
	)
	def test_line_oriented_goal() -> None:
	class OutputtingGoalOptions(LineOriented, GoalSubsystem):
	name = "dummy"
	class OutputtingGoal(Goal):
	subsystem_cls = OutputtingGoalOptions
	@goal_rule
	def output_rule(console: Console, options: OutputtingGoalOptions) -> OutputtingGoal:
	with options.output(console) as write_stdout:
	write_stdout("output...")
	with options.line_oriented(console) as print_stdout:
	print_stdout("line oriented")
	return OutputtingGoal(0)
	mock_console = MockConsole()
	# TODO: how should we mock `GoalSubsystem`s passed to `run_rule`?
	mock_options = Mock()
	mock_options.output = OutputtingGoalOptions.output
	mock_options.line_oriented = OutputtingGoalOptions.line_oriented
	result: OutputtingGoal = run_rule(output_rule, rule_args=[mock_console, mock_options])
	assert result.exit_code == 0
	assert mock_console.stdout.getvalue() == "output...line oriented"

If we use Mock, there, then we end up not even testing that GoalSubsystem works properly with Outputting becuase the Mock object won't be a real GoalSubsystem.

I won't block on this, and do appreciate trying to make testing a better experience, only don't want to put something in a public API until we explored other possibilities.

[cosmicexplorer]

I think the above argument is reasonable enough. Is it clear how to rewrite the tests in test_test.py in a way that uses a real GoalSubsystem, or would there need to be some separate infrastructure required to do that?

[Eric-Arellano]

Superseded by John creating a proper utility in #9528.