(Garden co-founder here)

Garden supports in-cluster building, using buildkit or kaniko.

This way, you don't need to have Docker or k8s running on your dev machine as you're working.

It also automates the process of redeploying services and re-running tests as you're coding (since it leverages the build/deploy/test dependencies in your stack).

We also provide hot reloading of running services, which brings a similarly fast feedback loop as with local dev.

The idea is to have a dev environment that has the same capabilities as the CI environment, and to be able to run any/all of your tests without having to go through your CI system (which generally involves a lot more waiting).