well each type of test should be in different db: yii2basic_functional, yii2basic_acceptance, yii2basic_unit (also very good when using CI http://codeception.com/05-24-2013/jenkins-ci-practice.html). Well, in acceptance and functional tests it is not very common to use db fixtures, because of we test like this:
1. load big dump with demo-data
2. run all tests.