A unit test framework tool is a tool that supports the creation, execution, and reporting of unit tests, which are tests that verify the functionality and quality of individual software components (such as functions or methods) in source code. A unit test framework tool can help to detect defects in functions or methods in source code by providing features such as test case generation, test case execution, test result comparison, test coverage measurement, etc. Some examples of unit test framework tools are JUnit, NUnit, TestNG, etc. The other options are not tools that are likely to detect defects in functions or methods in source code. A configuration management tool is a tool that supports the management and control of different versions and variants of software products or components. A test design tool is a tool that supports the design and generation of test cases based on some criteria or rules. A monitoring tool is a tool that monitors the behavior or performance of a system or component under test. Verified References: A Study Guide to the ISTQB® Foundation Level 2018 Syllabus - Springer, page 10.