For CI action: pre-build docker image with dependencies, then run your tests using this image as single GitHub action command. If dependencies change, rebuild i

For CI action: pre-build docker image with dependencies, then run your tests using this image as single GitHub action command. If dependencies change, rebuild image. Do not rely on gh caching, installs, multiple steps, etc. Otherwise there will be a moment when tests pass locally, but not on gh, and debugging will be super hard. In this case you just debug in the same image.