Imagine that we are writing a payroll system. This system has a number of functions.

• We can add employees to the payroll database.
• We can change existing employees.
• We can request that paychecks be created for a given payday.

Paychecks are output to a file in a simple text format.

We'd like to test this system. Here are a few acceptance tests to think about:

PayrollTests.AddAndPayTest	This test adds a few employees, pays them, and then checks to be sure that their paychecks are correct.
PayrollTests.ChangeBetweenTwoPaydays	This test adds some employees, pays them, then adds one more and changes an existing on. then pays again and checks to make sure the paychecks are correct.