Use the example in https://bugs.openjdk.java.net/browse/JDK-8138683

Misbehaviour A: not cancelling on Esc

- start editing such that the popup is open
- navigate by keyboard to a different item
- press esc
- expected: edit cancelled, that is value still same as in first column
- actual: edit committed, that is value changed to the item we navigated to

Misbehaviour B: not committing on Enter

- start editing such that the popup is not open (be sure the combo has focus)
- press up to select a different item
- press enter
- expected: value committed, editing terminated
- actual: nothing

These could be related to the fix of https://bugs.openjdk.java.net/browse/JDK-8138683, formally no regression because before the fix we couldn't navigate ;-)