Fixtures question - run *before* every test method?

I just noticed a behavior that makes me wonder exactly what the sequence
of events is when unit tests are run. All the stuff I’ve read says that
before every test method all the rows in the table get deleted and the
fixtures get ‘run’ to load the table. What I noticed today is that
after the execution of a test case, the table contents are exactly
what’s specified in the fixture. That leads me to wonder exactly what
triggers the execution of the code that uses the fixtures. Seems like
maybe the first execution is triggered by encountering a ‘def’ and after
that execution is triggered by encountering an ‘end’. Anybody know? Or
know where I should look?