Comment by mschuster91

> I would likely have already done that in the checkout and test part of my workflow, and can just copy everything over from that?

No you cannot, at least not for stuff that ships nodejs extensions to be compiled (e.g. by node-gyp). So for example if you're working on OS X and then run stuff in the Docker container you may hit errors. Additionally, if you are running e.g. on Ubuntu 18.04 and compile there and then run npm in a docker container on Ubuntu 16.04, you may hit library mismatches.