consider how to test the computation program from Section 3.3. Of course, you cannot try out all possible inputs of marital status and income level. Even if you could, there would be no point in trying them all. If the program correctly computes one or two tax amounts in a given bracket,then we have good reason to believe that all amounts will be correct.
You want to aim for complete coverage of all decision points. Here is a plan for obtaining a comprehensive set of test cases