There is a subtle issue happening in tests when we override a widget
property for the duration of the test and try to restore the initial state at
the end by rewriting on the property. It actually changes the widget, by
having a function bound to the sub widget prototype instead of its ancestor.
This in turns can cause weird interactions with the class system.
We introduced a proper way to temporarily patch a class/widget by adding
a method in testUtils to do exactly that. This commit simply uses that
method to prevent unwanted interactions in barcode tests
Géry Debongnie
0c98951f1c