Add customized app path testing to testbed.

No backends implement it yet.

Author: cyphase

android/tests_backend/app.py

@@ -25,7 +25,10 @@ def get_app_context(self):
         return self.native.getApplicationContext()
 
     @contextmanager
-    def prepare_paths(self):
+    def prepare_paths(self, *, custom):
+        if custom:
+            pytest.xfail("This backend doesn't implement app path customization.")
+
         yield {
             "config": Path(self.get_app_context().getFilesDir().getPath()) / "config",
             "data": Path(self.get_app_context().getFilesDir().getPath()) / "data",

cocoa/tests_backend/app.py

@@ -2,6 +2,7 @@
 from pathlib import Path
 
 import PIL.Image
+import pytest
 from rubicon.objc import SEL, NSPoint, ObjCClass, objc_id, send_message
 
 import toga
@@ -41,7 +42,10 @@ def is_cursor_visible(self):
         return self.app._impl._cursor_visible
 
     @contextmanager
-    def prepare_paths(self):
+    def prepare_paths(self, *, custom):
+        if custom:
+            pytest.xfail("This backend doesn't implement app path customization.")
+
         yield {
             "config": Path.home() / "Library/Preferences/org.beeware.toga.testbed",
             "data": Path.home()

gtk/tests_backend/app.py

@@ -30,7 +30,10 @@ def is_cursor_visible(self):
         pytest.skip("Cursor visibility not implemented on GTK")
 
     @contextmanager
-    def prepare_paths(self):
+    def prepare_paths(self, *, custom):
+        if custom:
+            pytest.xfail("This backend doesn't implement app path customization.")
+
         yield {
             "config": Path.home() / ".config/testbed",
             "data": Path.home() / ".local/share/testbed",

iOS/tests_backend/app.py

@@ -31,7 +31,10 @@ def get_path(self, search_path):
         return Path(urls[0].path)
 
     @contextmanager
-    def prepare_paths(self):
+    def prepare_paths(self, *, custom):
+        if custom:
+            pytest.xfail("This backend doesn't implement app path customization.")
+
         yield {
             "config": self.get_path(NSSearchPathDirectory.ApplicationSupport)
             / "Config",

testbed/tests/test_paths.py

@@ -5,8 +5,9 @@
 
 
 @pytest.mark.parametrize("attr", ["config", "data", "cache", "logs"])
-async def test_app_paths(app, app_probe, attr):
-    with app_probe.prepare_paths() as expected_paths:
+@pytest.mark.parametrize("custom", [False, True])
+async def test_app_paths(app, app_probe, attr, custom):
+    with app_probe.prepare_paths(custom=custom) as expected_paths:
         """Platform paths are as expected."""
         path = getattr(app.paths, attr)
         assert path == expected_paths[attr]

winforms/tests_backend/app.py

@@ -72,7 +72,10 @@ class CURSORINFO(ctypes.Structure):
         return info.hCursor is not None
 
     @contextmanager
-    def prepare_paths(self):
+    def prepare_paths(self, *, custom):
+        if custom:
+            pytest.xfail("This backend doesn't implement app path customization.")
+
         yield {
             "config": (
                 Path.home()