Skip cluster test on UDS, wire `tpt_proto` fixture

Add UDS skip-guard to `test_streaming_to_actor_cluster()`
and plumb `tpt_proto` through the `@tractor_test` wrapper
so transport-parametrized tests can receive it.

Deats,
- skip cluster test when `tpt_proto == 'uds'` with
  descriptive msg, add TODO about `@pytest.mark.no_tpt`.
- add `tpt_proto: str|None` param to inner wrapper in
  `tractor_test()`, forward to decorated fn when its sig
  accepts it.
- register custom `no_tpt` marker via `pytest_configure()`
  to avoid unknown-marker warnings.
- add masked todo for `no_tpt` marker-check code in `tpt_proto` fixture
  (needs fn-scope to work, left as TODO).
- add `request` param to `tpt_proto` fixture for future
  marker inspection.

Also,
- add doc-string to `test_streaming_to_actor_cluster()`.

(this commit msg was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code

tests/test_clustering.py

@@ -11,7 +11,6 @@ MESSAGE = 'tractoring at full speed'
 
 
 def test_empty_mngrs_input_raises() -> None:
-
     async def main():
         with trio.fail_after(3):
             async with (
@@ -60,8 +59,21 @@ async def worker(
         # assert 0
 
 
+# ?TODO, but needs a fn-scoped tpt_proto fixture..
+# @pytest.mark.no_tpt('uds')
 @tractor_test
-async def test_streaming_to_actor_cluster():
+async def test_streaming_to_actor_cluster(
+    tpt_proto: str,
+):
+    '''
+    Open an actor "cluster" using the (experimental) `._clustering`
+    API and conduct standard inter-task-ctx streaming.
+
+    '''
+    if tpt_proto == 'uds':
+        pytest.skip(
+            f'Test currently fails with tpt-proto={tpt_proto!r}\n'
+        )
 
     with trio.fail_after(6):
         async with (

tractor/_testing/pytest.py

@@ -74,6 +74,7 @@ def tractor_test(fn):
         reg_addr=None,
         start_method: str|None = None,
         debug_mode: bool = False,
+        tpt_proto: str|None=None,
         **kwargs
     ):
         # __tracebackhide__ = True
@@ -102,6 +103,9 @@ def tractor_test(fn):
             # set of subprocess spawning backends
             kwargs['debug_mode'] = debug_mode
 
+        if 'tpt_proto' in inspect.signature(fn).parameters:
+            # set of subprocess spawning backends
+            kwargs['tpt_proto'] = tpt_proto
 
         if kwargs:
 
@@ -177,6 +181,13 @@ def pytest_configure(config):
     backend = config.option.spawn_backend
     tractor._spawn.try_set_start_method(backend)
 
+    # register custom marks to avoid warnings see,
+    # https://docs.pytest.org/en/stable/how-to/writing_plugins.html#registering-custom-markers
+    config.addinivalue_line(
+        'markers',
+        'no_tpt(proto_key): test will (likely) not behave with tpt backend'
+    )
+
 
 @pytest.fixture(scope='session')
 def debug_mode(request) -> bool:
@@ -225,10 +236,26 @@ def tpt_protos(request) -> list[str]:
     autouse=True,
 )
 def tpt_proto(
+    request,
     tpt_protos: list[str],
 ) -> str:
     proto_key: str = tpt_protos[0]
 
+    # ?TODO, but needs a fn-scoped tpt_proto fixture..
+    # @pytest.mark.no_tpt('uds')
+    # node = request.node
+    # markers = node.own_markers
+    # for mark in markers:
+    #     if (
+    #         mark.name == 'no_tpt'
+    #         and
+    #         proto_key in mark.args
+    #     ):
+    #         pytest.skip(
+    #             f'Test {node} normally fails with '
+    #             f'tpt-proto={proto_key!r}\n'
+    #         )
+
     from tractor import _state
     if _state._def_tpt_proto != proto_key:
         _state._def_tpt_proto = proto_key