There are two problems with doing so as part of individual
functional tests:
1) If the application already have the value set the test will
time out waiting for a change that will never be made.
2) python-libjuju ``set_config`` call requires values to be
``str`` regardless of their actual type. Pairing this fact
with the requirement to use the actual type when comparing
values before attempting to set them makes this very confusing
and error prone.
juju/python-libjuju#388openstack-charmers/zaza#348
Use the ``config_change`` helper instead.
Frode Nordahl
9203865408