TestPageModel needs to be both is_abstract = True and Meta.abstract = True

wagtail/contrib/wagtailroutablepage/tests.py

@@ -148,6 +148,11 @@ class TestOldStyleRoutablePage(TestNewStyleRoutablePage, WagtailTestUtils):
             def main(self, request):
                 pass
 
+            # prevent this class appearing in the global PAGE_MODEL_CLASSES list, as
+            # its non-standard location causes failures when translating from content types
+            # back to models
+            is_abstract = True
+
             class Meta:
                 abstract = True