tests/py: Start the permission store

We now isolate the test environment so that the permission store will
start with an empty state but.

tests/__init__.py

@@ -341,6 +341,7 @@ def __init__(
         self.dbus_test_case = dbus_test_case
         self.portal_name = portal_name
         self.portal_frontend = None
+        self.permission_store = None
         self.dbus_monitor = None
         self.portal_interfaces: Dict[str, dbus.Interface] = {}
         self.app_id = app_id
@@ -444,6 +445,7 @@ def start_xdp(self):
 
         self.start_dbus_monitor()
         self.start_portal_frontend(env)
+        self.start_permission_store(env)
 
     def start_portal_frontend(self, env):
         # This roughly resembles test-portals.c and glib's test behavior
@@ -478,6 +480,43 @@ def start_portal_frontend(self, env):
 
         self.portal_frontend = portal_frontend
 
+    def start_permission_store(self, env):
+        """
+        Start the xdg-permission-store process
+        """
+
+        # This roughly resembles test-portals.c and glib's test behavior
+        # but preferences in-tree testing by running pytest in meson's
+        # project_build_root
+        libexecdir = os.getenv("LIBEXECDIR")
+        if libexecdir:
+            permission_store_path = Path(libexecdir) / "xdg-permission-store"
+        else:
+            permission_store_path = (
+                Path(os.getenv("G_TEST_BUILDDIR") or "tests")
+                / ".."
+                / "document-portal"
+                / "xdg-permission-store"
+             )
+
+        if not permission_store_path.exists():
+            raise FileNotFoundError(
+                f"{permission_store_path} does not exist, try running from meson build dir or setting G_TEST_BUILDDIR"
+            )
+
+        permission_store = subprocess.Popen([permission_store_path], env=env)
+
+        for _ in range(50):
+            if self.dbus_test_case.dbus_con.name_has_owner("org.freedesktop.impl.portal.PermissionStore"):
+                break
+            time.sleep(0.1)
+        else:
+            assert (
+                False
+            ), "Timeout while waiting for xdg-permission-store to claim the bus"
+
+        self.permission_store = permission_store
+
     def start_dbus_monitor(self):
         if not os.getenv("XDP_DBUS_MONITOR"):
             return
@@ -493,6 +532,10 @@ def tearDown(self):
             self.portal_frontend.terminate()
             self.portal_frontend.wait()
 
+        if self.permission_store:
+            self.permission_store.terminate()
+            self.permission_store.wait()
+
         for server in self.busses[dbusmock.BusType.SYSTEM]:
             self._terminate_mock_p (server.process)
         for server in self.busses[dbusmock.BusType.SESSION]: