Mark :insert-text with undo test as xfail on OS X

pytest.ini

@@ -20,6 +20,7 @@ markers =
     qtwebkit_skip: Tests not applicable with QtWebKit
     qtwebengine_createWindow: Tests using createWindow with QtWebEngine (QTBUG-54419)
     qtwebengine_flaky: Tests which are flaky (and currently skipped) with QtWebEngine
+    qtwebengine_osx_xfail: Tests which fail on OS X with QtWebEngine
 qt_log_level_fail = WARNING
 qt_log_ignore =
     ^SpellCheck: .*

tests/end2end/conftest.py

@@ -148,6 +148,8 @@ def pytest_collection_modifyitems(config, items):
          not config.webengine),
         ('qtwebengine_flaky', 'Flaky with QtWebEngine', pytest.mark.skipif,
          config.webengine),
+        ('qtwebengine_osx_xfail', 'Fails on OS X with QtWebEngine',
+         pytest.mark.xfail, config.webengine and sys.platform == 'darwin'),
     ]
 
     for item in items:

tests/end2end/features/yankpaste.feature

@@ -250,6 +250,7 @@ Feature: Yanking and pasting.
         # Compare
         Then the text field should contain "onHello worlde two three four"
 
+    @qtwebengine_osx_xfail
     Scenario: Inserting text into a text field with undo
         When I open data/paste_primary.html
         And I run :click-element id qute-textarea