Which of the following would be the LEAST likely to be used as the basis...

Test exit criteria are the conditions or requirements that must be met before testing can be concluded. Test exit criteria are usually defined in the test plan and agreed by the stakeholders. Test exit criteria can be based on various factors, such as test coverage, defect status, quality level, risk level, etc. Test schedules would be the least likely to be used as the basis for test exit criteria, because test schedules are not directly related to the quality or performance of the software product, but rather to the time or resources allocated for testing. Test schedules can be used as the basis for test entry criteria, which are the conditions or requirements that must be met before testing can start. The other options are more likely to be used as the basis for test exit criteria. Cost of testing performed so far can be used as a basis for test exit criteria, because it can indicate the return on investment or the cost-benefit ratio of testing. Confidence of testers in tested code can be used as a basis for test exit criteria, because it can reflect the level of satisfaction or assurance of the testers about the quality or reliability of the software product. Number of unfixed defects can be used as a basis for test exit criteria, because it can indicate the level of risk or impact of the remaining defects on the software product. Verified References: A Study Guide to the ISTQB® Foundation Level 2018 Syllabus - Springer, page 13.