In the previous example, a person must pay 10% income tax if his annual income is less than 30,000. A person must pay 15% income tax if his annual income is equal to or greater than 30,000. We now want to add a third assertion: If a person's annual income is greater than 100,000 he must pay 20% income tax.

We add another test case, which can be hard-coded into the test driver or inserted into the test case database:

Test Case 3:
Input: income = 200000
Output: tax = 40000

Notice the program being tested will fail Test 3 when this test case is first introduced. After the program is revised, it will satisfy this new test in the regression test.