Fixtures not loading?

My tests were all passing beautifully and then … they weren’t. Yes,
something changed: I pared tables relevant to this app out of a larger
application database. Now, however, when my fixtures (note plural)
method call occurs in test_helper.rb, it goes immediately to the
engines/lib/engines/testing_extensions.rb and fails at line 285,
claiming a nil object (nil.[]).

Stepping through this in rdebug shows this:

p file_names

[:users, :roles, :roles_users, :permissions, :permissions_roles]

So I know the fixture candidates are ok. But they are never loaded into
the test database and are not accessible via the accessor(:sym) method.

So, the following code always fails:

bogus_record = members(:existing_user_2)

as does

bogus_record = Member.find(:first)

Any thoughts?