#NEWLINE# def test_field_can_be_set_to_none( self ) : #NEWLINE# #INDENT# instance = create_instance ( Field ( ) ) #NEWLINE# instance . attr = 1234 #NEWLINE# instance . attr = None #NEWLINE# self . assertEqual ( None , self . attr ) #NEWLINE# self . assertFalse ( hasattr ( instance , '_attr' ) )