feat: Configuration option for setting default loop_scope for tests

New configuration option, asyncio_default_test_loop_scope, provides
default value for loop_scope argument of asyncio marker. This can be
used to use the same event loop in auto mode without need to use
modifyitems hook.

Test functions can still override loop_scope by using asyncio marker.

docs/how-to-guides/change_default_test_loop.rst

@@ -0,0 +1,24 @@
+=======================================================
+How to change the default event loop scope of all tests
+=======================================================
+The :ref:`configuration/asyncio_default_test_loop_scope` configuration option sets the default event loop scope for asynchronous tests. The following code snippets configure all tests to run in a session-scoped loop by default:
+
+.. code-block:: ini
+    :caption: pytest.ini
+
+    [pytest]
+    asyncio_default_test_loop_scope = session
+
+.. code-block:: toml
+    :caption: pyproject.toml
+
+    [tool.pytest.ini_options]
+    asyncio_default_test_loop_scope = "session"
+
+.. code-block:: ini
+    :caption: setup.cfg
+
+    [tool:pytest]
+    asyncio_default_test_loop_scope = session
+
+Please refer to :ref:`configuration/asyncio_default_test_loop_scope` for other valid scopes.

docs/how-to-guides/index.rst

@@ -9,10 +9,10 @@ How-To Guides
   migrate_from_0_23
   change_fixture_loop
   change_default_fixture_loop
+  change_default_test_loop
   run_class_tests_in_same_loop
   run_module_tests_in_same_loop
   run_package_tests_in_same_loop
-  run_session_tests_in_same_loop
   multiple_loops
   uvloop
   test_item_is_async

docs/reference/changelog.rst

@@ -2,9 +2,13 @@
 Changelog
 =========
 
-0.25.2 (2025-01-08)
+0.26.0 (UNRELEASED)
 ===================
+- Adds configuration option that sets default event loop scope for all testss `#793 <https://github.com/pytest-dev/pytest-asyncio/issues/793>`_
+
 
+0.25.2 (2025-01-08)
+===================
 - Call ``loop.shutdown_asyncgens()`` before closing the event loop to ensure async generators are closed in the same manner as ``asyncio.run`` does `#1034 <https://github.com/pytest-dev/pytest-asyncio/pull/1034>`_
 
 0.25.1 (2025-01-02)

docs/reference/configuration.rst

@@ -8,6 +8,12 @@ asyncio_default_fixture_loop_scope
 ==================================
 Determines the default event loop scope of asynchronous fixtures. When this configuration option is unset, it defaults to the fixture scope. In future versions of pytest-asyncio, the value will default to ``function`` when unset. Possible values are: ``function``, ``class``, ``module``, ``package``, ``session``
 
+.. _configuration/asyncio_default_test_loop_scope:
+
+asyncio_default_test_loop_scope
+===============================
+Determines the default event loop scope of asynchronous tests. When this configuration option is unset, it default to function scope. Possible values are: ``function``, ``class``, ``module``, ``package``, ``session``
+
 asyncio_mode
 ============
 The pytest-asyncio mode can be set by the ``asyncio_mode`` configuration option in the `configuration file

pytest_asyncio/plugin.py

@@ -107,6 +107,12 @@ def pytest_addoption(parser: Parser, pluginmanager: PytestPluginManager) -> None
         help="default scope of the asyncio event loop used to execute async fixtures",
         default=None,
     )
+    parser.addini(
+        "asyncio_default_test_loop_scope",
+        type="string",
+        help="default scope of the asyncio event loop used to execute tests",
+        default="function",
+    )
 
 
 @overload
@@ -217,9 +223,15 @@ def pytest_configure(config: Config) -> None:
 def pytest_report_header(config: Config) -> list[str]:
     """Add asyncio config to pytest header."""
     mode = _get_asyncio_mode(config)
-    default_loop_scope = config.getini("asyncio_default_fixture_loop_scope")
+    default_fixture_loop_scope = config.getini("asyncio_default_fixture_loop_scope")
+    default_test_loop_scope = _get_default_test_loop_scope(config)
+    header = [
+        f"mode={mode}",
+        f"asyncio_default_fixture_loop_scope={default_fixture_loop_scope}",
+        f"asyncio_default_test_loop_scope={default_test_loop_scope}",
+    ]
     return [
-        f"asyncio: mode={mode}, asyncio_default_fixture_loop_scope={default_loop_scope}"
+        "asyncio: " + ", ".join(header),
     ]
 
 
@@ -807,7 +819,8 @@ def pytest_generate_tests(metafunc: Metafunc) -> None:
     marker = metafunc.definition.get_closest_marker("asyncio")
     if not marker:
         return
-    scope = _get_marked_loop_scope(marker)
+    default_loop_scope = _get_default_test_loop_scope(metafunc.config)
+    scope = _get_marked_loop_scope(marker, default_loop_scope)
     if scope == "function":
         return
     event_loop_node = _retrieve_scope_root(metafunc.definition, scope)
@@ -1078,7 +1091,8 @@ def pytest_runtest_setup(item: pytest.Item) -> None:
     marker = item.get_closest_marker("asyncio")
     if marker is None:
         return
-    scope = _get_marked_loop_scope(marker)
+    default_loop_scope = _get_default_test_loop_scope(item.config)
+    scope = _get_marked_loop_scope(marker, default_loop_scope)
     if scope != "function":
         parent_node = _retrieve_scope_root(item, scope)
         event_loop_fixture_id = parent_node.stash[_event_loop_fixture_id]
@@ -1108,7 +1122,9 @@ def pytest_runtest_setup(item: pytest.Item) -> None:
 """
 
 
-def _get_marked_loop_scope(asyncio_marker: Mark) -> _ScopeName:
+def _get_marked_loop_scope(
+    asyncio_marker: Mark, default_loop_scope: _ScopeName
+) -> _ScopeName:
     assert asyncio_marker.name == "asyncio"
     if asyncio_marker.args or (
         asyncio_marker.kwargs and set(asyncio_marker.kwargs) - {"loop_scope", "scope"}
@@ -1119,12 +1135,18 @@ def _get_marked_loop_scope(asyncio_marker: Mark) -> _ScopeName:
             raise pytest.UsageError(_DUPLICATE_LOOP_SCOPE_DEFINITION_ERROR)
         warnings.warn(PytestDeprecationWarning(_MARKER_SCOPE_KWARG_DEPRECATION_WARNING))
     scope = asyncio_marker.kwargs.get("loop_scope") or asyncio_marker.kwargs.get(
-        "scope", "function"
+        "scope"
     )
+    if scope is None:
+        scope = default_loop_scope
     assert scope in {"function", "class", "module", "package", "session"}
     return scope
 
 
+def _get_default_test_loop_scope(config: Config) -> _ScopeName:
+    return config.getini("asyncio_default_test_loop_scope")
+
+
 def _retrieve_scope_root(item: Collector | Item, scope: str) -> Collector:
     node_type_by_scope = {
         "class": Class,

tests/test_asyncio_mark.py

@@ -146,3 +146,80 @@ async def test_a():
     result.stdout.fnmatch_lines(
         ["*Tests based on asynchronous generators are not supported*"]
     )
+
+
+def test_asyncio_marker_fallbacks_to_configured_default_loop_scope_if_not_set(
+    pytester: Pytester,
+):
+    pytester.makeini(
+        dedent(
+            """\
+            [pytest]
+            asyncio_default_fixture_loop_scope = function
+            asyncio_default_test_loop_scope = session
+            """
+        )
+    )
+
+    pytester.makepyfile(
+        dedent(
+            """\
+            import asyncio
+            import pytest_asyncio
+            import pytest
+
+            loop: asyncio.AbstractEventLoop
+
+            @pytest_asyncio.fixture(loop_scope="session", scope="session")
+            async def session_loop_fixture():
+                global loop
+                loop = asyncio.get_running_loop()
+
+            async def test_a(session_loop_fixture):
+                global loop
+                assert asyncio.get_running_loop() is loop
+            """
+        )
+    )
+
+    result = pytester.runpytest("--asyncio-mode=auto")
+    result.assert_outcomes(passed=1)
+
+
+def test_asyncio_marker_uses_marker_loop_scope_even_if_config_is_set(
+    pytester: Pytester,
+):
+    pytester.makeini(
+        dedent(
+            """\
+            [pytest]
+            asyncio_default_fixture_loop_scope = function
+            asyncio_default_test_loop_scope = module
+            """
+        )
+    )
+
+    pytester.makepyfile(
+        dedent(
+            """\
+            import asyncio
+            import pytest_asyncio
+            import pytest
+
+            loop: asyncio.AbstractEventLoop
+
+            @pytest_asyncio.fixture(loop_scope="session", scope="session")
+            async def session_loop_fixture():
+                global loop
+                loop = asyncio.get_running_loop()
+
+            @pytest.mark.asyncio(loop_scope="session")
+            async def test_a(session_loop_fixture):
+                global loop
+                assert asyncio.get_running_loop() is loop
+            """
+        )
+    )
+
+    result = pytester.runpytest("--asyncio-mode=auto")
+    result.assert_outcomes(passed=1)