testing: define and use all fixture methods.
When a helper suite defines only a subset of the available
fixture methods, it invites problems if that subset changes.
By making all helper suites define all fixture methods,
we make it easy to mechanically check that
a helper suite is being used correctly without going
to look at the source for that suite.
R=niemeyer
CC=
https://codereview.appspot.com/6472053