Update config page test to new API

* Return value of `.create_checkbox()` changed in spyder-ide/spyder#20926
  (Show tooltips in Preferences).
* Handling of Prefs dialog box size changed in spyder-ide/spyder#21233
  (Improve style of Preferences dialog box).

spyder_unittest/widgets/confpage.py

@@ -24,8 +24,9 @@ class UnitTestConfigPage(PluginConfigPage):
 
     def setup_page(self) -> None:
         settings_group = QGroupBox(_('Settings'))
-        self.abbrev_box = self.create_checkbox(
+        widget = self.create_checkbox(
             _('Abbreviate test names'), 'abbrev_test_names', default=False)
+        self.abbrev_box = widget.checkbox
 
         settings_layout = QVBoxLayout()
         settings_layout.addWidget(self.abbrev_box)

spyder_unittest/widgets/tests/test_confpage.py

@@ -71,9 +71,6 @@ def get_plugin(self, plugin_name, error=True):
         if plugin_name in PLUGIN_REGISTRY:
             return PLUGIN_REGISTRY.get_plugin(plugin_name)
 
-    def set_prefs_size(self, size):
-        pass
-
 
 class ConfigDialogTester(QWidget):
     def __init__(self, parent, main_class,
@@ -83,9 +80,6 @@ def __init__(self, parent, main_class,
         if self._main is None:
             self._main = MainWindowMock(self)
 
-        def set_prefs_size(self, size):
-            pass
-
         def register_plugin(self, plugin_name, external=False):
             plugin = PLUGIN_REGISTRY.get_plugin(plugin_name)
             plugin._register()
@@ -101,8 +95,6 @@ def get_plugin(self, plugin_name, error=True):
         #         types.MethodType(register_plugin, self._main))
         setattr(self._main, 'get_plugin',
                 types.MethodType(get_plugin, self._main))
-        setattr(self._main, 'set_prefs_size',
-                types.MethodType(set_prefs_size, self._main))
 
         PLUGIN_REGISTRY.reset()
         PLUGIN_REGISTRY.sig_plugin_ready.connect(self._main.register_plugin)
@@ -135,7 +127,7 @@ def config_dialog(qtbot, request):
     qtbot.addWidget(main_ref)
 
     preferences = main_ref._main.get_plugin(Plugins.Preferences)
-    preferences.open_dialog(None)
+    preferences.open_dialog()
     container = preferences.get_container()
     dlg = container.dialog