As computer users increasingly rely on digital tools for daily tasks, the complexity of their working environments continues to grow. Modern knowledge workers must navigate a diverse array of digital resources, including documents, websites, applications, and other information. This complexity presents challenges in managing multiple activities to maintain productivity, such as handling interruptions, resuming tasks, curating resources, recalling context, retrieving previously closed digital resources, and fostering self-reflection. Despite these challenges, there has been limited research on leveraging visual cues to help users reconstruct their previous mental contexts, retrieve digital resources, and enhance self-reflection for behavioral change. Therefore, this Ph.D. dissertation addresses these gaps by focusing on: (1) investigating the existing challenges users face in curating digital resources, (2) designing and implementing supportive applications for task resumption, (3) developing methods that utilize screenshots and metadata for reconstructing mental context and retrieving resources, and (4) enhancing the processes of self-reflection and behavioral change to improve overall productivity. / Doctor of Philosophy / In our increasingly digital world, people are spending more time on computers to complete their daily tasks. However, as there are increasing resources and information involved, managing tasks has become more complex because individuals need to juggle various digital tools at the same time, like documents, websites, and applications. This can lead to difficulties such as dealing with interruptions, picking up where they left off, organizing information, remembering what they were working on, and reflecting on their habits to make positive changes. Surprisingly, there has been little research on how common-seen visual tools, like screenshots, can help people better handle these challenges. Screenshots can serve as visual reminders, helping users remember what they were doing and easily find the resources they need. Hence, this Ph.D. dissertation explores these issues by: (1) examining the problems people face when organizing digital resources, (2) creating tools to help users quickly resume their tasks, (3) using screenshots and additional information to help users remember their previous work, and (4) improving the way people reflect on their behavior to encourage positive changes.

The aim of the thesis was to design, implement and evaluate the results of automatic tests for the JavaScript Restrictor project, which is being developed as a web browser extension. The tests are divided into three levels - unit, integration, and system. The Unit Tests verify the behavior of individual features, the Integration Tests verify the correct wrapping of browser API endpoints, and the System Tests check that the extension does not suppress the desired functionality of web pages. The System Tests are implemented for parallel execution in a distributed environment which has succeeded in achieving an almost directly proportional reduction in time with respect to the number of the tested nodes. The benefit of this work is detection of previously unknown errors in the JavaScript Restrictor extension and provision of the necessary information that allowed to fix some of the detected bugs.