Tim Ebert

> refactor remaining controllers to `reconcile.Reconciler` interface (extensions controller: controllerinstallation/shootstate) I tried to accomplish this, but I faced a few difficulties with the current implementation/architecture of the package: - the...

> check whether we can remove active worker counting in our controllers (dummy graceful termination) I look into this and played around with it a little bit. The result: -...

/assign @rfranzke @timebertt

In addition to the mentioned tests we could - [x] make use of [go-apidiff](https://github.com/joelanford/go-apidiff) to easily detect breaking changes in signatures of the extensions library (see https://github.com/kubernetes-sigs/controller-runtime/blob/master/hack/apidiff.sh for an example...

We should definitely - [x] add missing unit tests for the predicates provided by the extensions library (e.g. [`AddTypePredicate`](https://github.com/gardener/gardener/blob/092922b5765ad5e84cc93a40c87c5a80e5841023/extensions/pkg/predicate/predicate.go#L164) is untested but used in all extension controllers) ->tracked in https://github.com/gardener/gardener/pull/6249

We need integration tests for - [ ] the extension webhooks (start a manager, register webhooks using the extensions library, do some dummy mutations, assert that they are applied, ...)...

> kupid [Can't be done as it needs old version of controller-gen tool] @acumino Why is that? The controller-tools version is controlled via the project's `go.mod`. I expect that you...

And what about installing the old version of the tool, that still has the flag, i.e. v0.6.2 (ref https://github.com/gardener/kupid/blob/db5a7ddd0e4133df1ecbf22dda24aa7188422f74/Makefile#L13)?

The rule will install the version specified in `go.mod` 🤔

@jia-jerry @EmoinLanyu I don't see any reaction on the general concerns raised by @vlerenc and me or justification for the motivation behind this GEP. If there is no such feedback...