This study presents a comprehensive comparison of software quality assurance techniques across several software development methodologies. It addresses critical knowledge gaps by examining the application of quality assurance processes, associated challenges, and outcomes in diverse software development contexts. The study covers a wide spectrum of development approaches, including classical Waterfall procedures and Agile alternatives such as Scrum, Kanban, Iterative, and Extreme Programming. The research delves into the responsibilities, experiences, and domains of experts involved in these approaches, providing valuable insights into the realm of software development approaches. Key findings of the study underscore the pervasive use of core testing approaches such as regression testing, unit testing, integration testing, performance testing, and security testing. The study also emphasizes the importance of guaranteeing requirement traceability, as well as providing insights on the technologies utilized for this purpose. Moreover, the research highlights the critical importance of achieving comprehensive test coverage and provides insights into a range of techniques for accomplishing this goal. The paper discusses the challenges encountered while testing complicated or interconnected software systems and offers practical solutions such as shift-left testing and exploratory testing to mitigate them. Notably, it highlights the substantial financial benefits derived from effective quality assurance processes, including reduced defect-fixing costs, minimized rework, optimized resource utilization, and heightened customer retention. Moreover, the paper delves into cost-effective quality assurance solutions and assesses the impact of quality assurance practices on user experience and customer satisfaction.