in my odoo  survey.survey inherits from abstract model where a field is added :

_ruid = fields.Char('ruid', default=False, index=True, store=True)

the value is generated by a  uuid.uuid4() after init on create 

i try to get the _ruid field from a survey record i get error :

AttributeError: 'survey.survey' object has no attribute '_ruid'

on the other hand if i run an Sql query it's there and i can access it just fine

self.env.cr.execute("select _ruid from survey_survey where id=4​"

PS: this only happens when i run server in test mode. (part of transaction case test ) 

where is the problem ?