Expose `tractor_test` in the same way as `trio`

tests/conftest.py

@@ -5,7 +5,7 @@ import random
 
 import pytest
 import tractor
-from tractor._tractor_test import tractor_test
+from tractor.testing import tractor_test
 
 
 pytest_plugins = ['pytester']

tractor/testing/__init__.py

@@ -0,0 +1 @@
+from ._tractor_test import tractor_test

tractor/testing/_tractor_test.py

@@ -1,7 +1,10 @@
 import inspect
 from functools import partial, wraps
 
-from . import run
+from .. import run
+
+
+__all__ = ['tractor_test']
 
 
 def tractor_test(fn):