I stay with the toy story named releases. That way I never get a surprise upgrade when the meaning of "testing" changes. You almost never want that, since when the name changes it is the early days of testing.
Later when I need something from the next release, I'll upgrade to its name.
I think he means that he has 'jessie' listed in sources.list, rather than 'testing'. The latter will refer to a different version when jessie becomes stable, and again when the next one becomes stable.
Later when I need something from the next release, I'll upgrade to its name.