Serendipitous Architecture

Note the pressure that the acceptance tests placed on the architecture of the payroll system. The very fact that we considered the tests first led us to the notion of an API for the functions of the payroll system. Clearly, the UI will use this API to achieve its ends. Note also that the printing of the paychecks must be decoupled from the Create Paychecks function. These are good architectural decisions.

Figure 4-3. Sample acceptance test