diff --git a/tests/unit/conftest.py b/tests/unit/auto_resource_test_plugin.py
similarity index 57%
rename from tests/unit/conftest.py
rename to tests/unit/auto_resource_test_plugin.py
index 869fbb02..336978b9 100644
--- a/tests/unit/conftest.py
+++ b/tests/unit/auto_resource_test_plugin.py
@@ -1,4 +1,4 @@
-"""Fixtures shared by focused unit-test modules."""
+"""Pytest fixtures loaded only by the auto-resource test modules."""
 
 from .auto_resource_test_support import auto_resource_env
 
diff --git a/tests/unit/test_auto_image_steps.py b/tests/unit/test_auto_image_steps.py
index 44defb75..1e4c9d87 100644
--- a/tests/unit/test_auto_image_steps.py
+++ b/tests/unit/test_auto_image_steps.py
@@ -49,6 +49,8 @@ from .auto_resource_test_support import (
     write_note as _write_note,
 )
 
+pytest_plugins = ("unit.auto_resource_test_plugin",)
+
 
 @pytest.mark.parametrize(
     ("image_format", "suffix", "source_mime", "request_mime"),
diff --git a/tests/unit/test_auto_resource_review_regressions.py b/tests/unit/test_auto_resource_review_regressions.py
index e4dc307c..5b8a1d4b 100644
--- a/tests/unit/test_auto_resource_review_regressions.py
+++ b/tests/unit/test_auto_resource_review_regressions.py
@@ -12,6 +12,7 @@ from .auto_resource_test_support import (
     write_note,
 )
 
+pytest_plugins = ("unit.auto_resource_test_plugin",)
 pytestmark = pytest.mark.asyncio