This paper deals with software quality assurance. Selected standards of the quality management system are listed and described, starting from the general ones (ISO standards) to those applied for the field of software development (CMMI, TMMI and CISQ). Organizations implement different standards to improve the quality of their software. Functional and non-functional quality requirements are described according to which the software is analyzed for the purpose of correctness. The criteria for measuring software quality is listed, with focus on product aspect, process and project quality.. There are different models or approaches that can be used in the software development process where each model has its advantages and disadvantages. The advantages and disadvantages of the most common development models are explained - Waterfall, Spiral, V- model, Agile and Iterative. The quality of any software can only be known through testing. Software testing is the process of running a software program or application and finding bugs in that program or application. With the advancement of technology around the world, the number of software testing techniques and methods has increased. Testing of software in its development is presented below, where the types, levels and principles of testing are explained in more detail. Quality control experts analyze test results and find errors. They are responsible for identifying and eliminating defects in the product.