The SDLC (Software Development Life Cycle) is an approach to software development that has been around for a long time. It consists of six phases: In the STLC (Software Testing Life Cycle), testing is the main activity. This approach focuses on the quality of the product, but it is not specific to software development. The main goal of SDLC and STLC are to make sure that a product will be developed in a way that it will be useful for its users. As such, they are used in different industries like automotive, medical devices, IT and so on.