A Mobile Applications Testing Developer is responsible for conducting automated and manual tests to ensure the software created by developers is fit for purpose. They assess software quality through manual and automated testing, responsible for finding and reporting bugs and glitches. They run tests to ensure the applications are user-friendly, effective, and reliable. They design and implement testing protocols, analyze the results, identify issues, and report their findings to development teams. They also ensure that the final product can handle the required tasks in real-world scenarios, thus ensuring the quality of mobile applications before they reach users.