[pygobject] Add a test scroll event attr mapping

[Christoph Reiter <creiter src gnome org>]

commit 2bb9b5d317144b0f07eb0b3fdf305b3411641476
Author: Christoph Reiter <reiter christoph gmail com>
Date:   Fri Apr 17 16:20:00 2020 +0200

    Add a test scroll event attr mapping

 tests/test_overrides_gdk.py | 5 +++++
 1 file changed, 5 insertions(+)
---
diff --git a/tests/test_overrides_gdk.py b/tests/test_overrides_gdk.py
index d49cdcf3..1788ef61 100644
--- a/tests/test_overrides_gdk.py
+++ b/tests/test_overrides_gdk.py
@@ -123,6 +123,11 @@ class TestGdk(unittest.TestCase):
         event.type = Gdk.EventType.SCROLL
         self.assertRaises(AttributeError, lambda: getattr(event, 'foo_bar'))
 
+    @unittest.skipIf(GDK4, "not in gdk4")
+    def test_scroll_event(self):
+        event = Gdk.Event.new(Gdk.EventType.SCROLL)
+        assert event.direction == Gdk.ScrollDirection.UP
+
     @unittest.skipIf(GDK4, "not in gdk4")
     def test_event_strip_boolean(self):
         ev = Gdk.EventButton()