In HBT, the test design comments with identifying the level for which the tests to be conducted and the identifying the entities at each level.
As mentioned above in agile context, we consider FOUR types of entities for test.
E1 – A user story
E2 – A Collection of user stories
E3 – A usage flow that constitutes a set of user stories
E4 – Set of user stories across releases/sprints/epics – bigger flow
The basic user story (E1) may be made up of a set of screens, APIs or command line which accepts inputs and hence level 1,2,3 as well as basic behavior (L4) of the end user also is applicable.
A set of user stories form an epic, for which behavior correctness (L4) is indeed applicable.
A set of user stories that form a flow (E3) has to be checked for flow correctness and attributes.
The higher order entities (E3/E4) consisting of aggregation of user stories which can be within the sprint or across the sprint make bigger flows. The focus of tests and test cases for these entities fall under L5-L8.