allow passing in args constructors to ensure that all widgets are cre…

…ated on the same thread

testbed/tests/widgets/conftest.py

@@ -1,5 +1,6 @@
 import gc
 import weakref
+from typing import Callable, Iterable, ParamSpec, Union
 from unittest.mock import Mock
 
 from pytest import fixture
@@ -10,6 +11,8 @@
 from ..conftest import skip_on_platforms, xfail_on_platforms
 from .probe import get_probe
 
+P = ParamSpec("P")
+
 
 @fixture
 async def widget():
@@ -84,18 +87,27 @@ def verify_vertical_alignment():
 
 
 def build_cleanup_test(
-    widget_class, args=None, kwargs=None, skip_platforms=(), xfail_platforms=()
+    widget_constructor: Callable[[P], toga.Widget],
+    args: Union[P.args, Callable[..., P.args]] = (),
+    kwargs: Union[P.kwargs, Callable[..., P.args], None] = None,
+    skip_platforms: Iterable[str] = (),
+    xfail_platforms: Iterable[str] = (),
 ):
     async def test_cleanup():
         nonlocal args, kwargs
 
         skip_on_platforms(*skip_platforms)
         xfail_on_platforms(*xfail_platforms, reason="Leaks memory")
 
-        widget = widget_class(
-            *(args if args is not None else ()),
-            **(kwargs if kwargs is not None else {}),
-        )
+        if callable(args):
+            args = args()
+
+        if callable(kwargs):
+            kwargs = kwargs()
+        elif args is None:
+            kwargs = {}
+
+        widget = widget_constructor(*args, **kwargs)
         ref = weakref.ref(widget)
 
         # Args or kwargs may hold a backref to the widget itself, for example if they

testbed/tests/widgets/test_optioncontainer.py

@@ -74,7 +74,7 @@ async def widget(content1, content2, content3, on_select_handler):
 
 test_cleanup = build_cleanup_test(
     toga.OptionContainer,
-    kwargs={"content": [("Tab 1", toga.Box())]},
+    kwargs=lambda: {"content": [("Tab 1", toga.Box())]},
     xfail_platforms=("android", "iOS", "linux"),
 )
 

testbed/tests/widgets/test_scrollcontainer.py

@@ -75,7 +75,7 @@ async def widget(content, on_scroll):
 
 test_cleanup = build_cleanup_test(
     toga.ScrollContainer,
-    kwargs={"content": toga.Box()},
+    kwargs=lambda: {"content": toga.Box()},
     xfail_platforms=("android", "iOS", "linux"),
 )
 

testbed/tests/widgets/test_splitcontainer.py

@@ -63,7 +63,7 @@ async def widget(content1, content2):
 
 test_cleanup = build_cleanup_test(
     toga.SplitContainer,
-    kwargs={"content": [toga.Box(), toga.Box()]},
+    kwargs=lambda: {"content": [toga.Box(), toga.Box()]},
     skip_platforms=("android", "iOS"),
 )