In HBT, the test design activity is done quality level-wise and within each level in two stages, design test scenarios first and then test cases. The act of test design commences with the identification of the test level and then specific type of test for which the test scenarios and cases to be designed.
Having identified the test entities it is then required to partition the problem into two parts: firstly to understand the behaviour (business logic) and then to understand the various data elements for the business logic. This allows us to identify the various conditions in the business logic and allow us to model the behaviour more formally. The behaviour model is used to generate test scenarios. Then for every given scenario, we have to understand the data elements that vary and then come up with the optimal number of values for each data element. The various values of each data element are then combined to generate the test cases.