I am a newbie for operator-sdk. Now I am writing test for operator with envtest framework, so I had a fake control-plane for environments.
Inside controller reconcile loop, once I initialize a CR, then controller will pull down an image for pod and deploy that Pod.
All behaviour in the above happens in the real k8s cluster. My question is, under envtest environemnts, does controller really pull down image for deploying Pods?
That depends on envtest configuration. Here is quotes from kubebuilder book:
envtest setting up and starting an instance of etcd and the Kubernetes API server, without kubelet, controller-manager or other components
Unless you’re using an existing cluster, keep in mind that no built-in controllers are running in the test context
So, if you don't set USE_EXISTING_CLUSTER env var to true, envtest will set control plane with only API server and etcd. For example, if your controller should create Deployment at some event, there's no deployment controller in test environment that gonna create ReplicaSet and Pods. Basically, all it does is stores state of test environment in etcd.