Add more abstracted resources as currently only Command tests is provided.

I stumbled upon this framework while doing research for containers acceptance testing needs. I used [dgoss](https://github.com/aelsabbahy/goss/tree/master/extras/dgoss) for my containers acceptance testing needs till now and love the resources provided by its underlying [goss](https://github.com/aelsabbahy/goss) which are great for the cloud native IAC pipelines. On other hand, I loved the Metadata test functionality from this project. Logically, it makes sense to add more abstracted resources like goss in this tool to make it one stop lightweight declarative framework for the containers unit testing. Any thoughts on this request?