Being the developer of testing tools used for automation is likely to develop the necessary skills to effectively test a software system because it involves a deep understanding of testing processes and the creation of tools that facilitate these processes. This experience provides insight into the intricacies of test automation, which is crucial for designing effective tests and ensuring thorough coverage of the system under test.
References: The current page suggests referring to the ISTQB Advanced Level Test Manager Syllabus and other ISTQB documents for a comprehensive understanding of the roles and skills required for effective software testing. It emphasizes the importance of alignment of methodologies in distributed testing models, which is relevant to the development and use of testing tools.