Tang Chen b58dd4f17f [Volume] Check return value is None in volume unit tests
take_action() in commands inheriting from Command returns nothing.
So we should assert the return is None in the unit tests of these
commands.

Change-Id: Idd961a5fa3db825353700837a559621d17f782c5
Partial-Bug: #1550636
2016-03-03 21:07:08 +08:00
..
2014-01-20 17:28:13 +04:00
2015-04-15 22:40:52 -05:00