search for: test_not_owner

I''m following Agile Edition 1. On page 148 it suggests using instance variables named after the fixture, for example: assert_equal @version_control_book.id, @product.id When I introduce this type of instance variable into my test, I get the following error: 1) Error: test_not_owner(GroupTest): RuntimeError: Called id for nil, which would mistakenly be 4 -- if you really wanted the id of nil, use object_id test/unit/group_test.rb:8:in `setup_without_fixtures'' /usr/local/lib/ruby/gems/1.8/gems/activerecord-1.14.2/lib/active_record/fixtures.rb:548:in `setup...