[py] Use XWayland for internal Python Firefox tests

py/conftest.py

@@ -154,6 +154,9 @@ def fin():
     if driver_instance is None:
         if driver_class == "Firefox":
             options = get_options(driver_class, request.config)
+            # There are issues with window size/position when running Firefox
+            # under Wayland, so we use XWayland instead.
+            os.environ["MOZ_ENABLE_WAYLAND"] = "0"
         if driver_class == "Chrome":
             options = get_options(driver_class, request.config)
         if driver_class == "Edge":
@@ -166,6 +169,9 @@ def fin():
             options = get_options("Firefox", request.config) or webdriver.FirefoxOptions()
             options.set_capability("moz:firefoxOptions", {})
             options.enable_downloads = True
+            # There are issues with window size/position when running Firefox
+            # under Wayland, so we use XWayland instead.
+            os.environ["MOZ_ENABLE_WAYLAND"] = "0"
         if driver_path is not None:
             kwargs["service"] = get_service(driver_class, driver_path)
         if options is not None:

py/test/selenium/webdriver/firefox/firefox_sizing_tests.py

@@ -0,0 +1,64 @@
+# Licensed to the Software Freedom Conservancy (SFC) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The SFC licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+import os
+import platform
+from unittest.mock import patch
+
+import pytest
+
+from selenium import webdriver
+from selenium.webdriver.firefox.options import Options
+
+
+def is_running_wayland():
+    if platform.system() == "Linux" and os.getenv("WAYLAND_DISPLAY"):
+        return True
+    return False
+
+
+@pytest.mark.skipif(not is_running_wayland(), reason="This test only runs on Linux under Wayland")
+def test_firefox_opens_large_when_running_xwayland(request):  # noqa: F821
+    options = Options()
+    if request.config.getoption("--headless"):
+        options.add_argument("-headless")
+    # setting environment variable `MOZ_ENABLE_WAYLAND=0` forces Firefox
+    # to run under XWayland on Wayland based systems
+    with patch.dict("os.environ", {"MOZ_ENABLE_WAYLAND": "0"}):
+        try:
+            driver = webdriver.Firefox(options=options)
+            size = driver.get_window_size()
+            assert size["height"] > 500
+            assert size["width"] > 500
+        finally:
+            driver.quit()
+
+
+@pytest.mark.skipif(not is_running_wayland(), reason="This test only runs on Linux under Wayland")
+@pytest.mark.xfail(reason="https://bugzilla.mozilla.org/show_bug.cgi?id=1959040")
+# Firefox opens in a small window when running on Linux/Wayland
+def test_firefox_opens_large_when_running_wayland(request):  # noqa: F821
+    options = Options()
+    if request.config.getoption("--headless"):
+        options.add_argument("-headless")
+    try:
+        driver = webdriver.Firefox(options=options)
+        size = driver.get_window_size()
+        assert size["height"] > 500
+        assert size["width"] > 500
+    finally:
+        driver.quit()