Which statement about the test-data approach in a computerized system is NOT true?

• A. The test data need consist of only those valid and invalid conditions in which the auditor is interested
• B. Only one transaction of each type need be tested
• C. Test data are processed by the client's computer programs under the auditor's control
• D. The test data must consist of all possible valid and invalid conditions

Answer: (D)

The test-data approach relies on feeding a carefully chosen set of valid and invalid inputs into the client’s programs, under the auditor’s control, to observe whether the system processes correctly and handles errors. Since trying every possible input is usually impossible, testers select representative cases, including edge conditions, to reveal processing defects. Therefore, requiring all possible valid and invalid conditions is not true. The other statements fit the method: you target conditions of interest, the data are processed on the client’s system under auditor control, and you typically test more than one transaction per type to explore different paths and ensure consistency.