In a nutshell, Agile in game development means dividing the process of game creation into short iterations. Thus, instead of working on the whole project from the very beginning to the release, the development team works on small projects which are normally called features. 

As developers write code, they can build unit testing modules directly into the code to ensure that by the time a piece of software has moved through the DevOps lifecycle, it has already been tested against most scenarios. If done correctly, this is a very efficient way to test code. Building testing modules into code requires that a fair process is in place to ensure that testing occurs throughout the entire process. Once done, this module can perform some of the duties required from a QA tester.