It is worth keeping in mind how a Docker application is defined. At its most basic level, a Docker application is really no different from any software project. It is simply a Dockerfile and the resources needed for the image are most likely stored in version control. It is software.
Treating Docker applications like code means that an administrator or team of administrators can benefit from all of the advances in software development methodologies. One of those is the automated building and testing of a project. This process is called CI. Any time a change is made to an application, whether it is a small change to a configuration file or the upgrade of the actual application, the image can be automatically rebuilt and tested to ensure that the image will work as intended when it is deployed.
I often joke that my job as a system administrator is to get other people or things to do my work for me. The reality is that the more I can empower other people in my organization...