Fix boilerplate and make stub controller

pkg/admission/admission_control.go

@@ -17,19 +17,34 @@ limitations under the License.
 package admission
 
 import (
+	"errors"
+
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/client"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/runtime"
 )
 
-// alwaysAdmitController says yes to all admission control requests, its useful for testing.
-type alwaysAdmitController struct{}
+// stubAdmissionController is capable of either always admitting or always denying incoming requests
+type stubAdmissionController struct {
+	admit bool
+}
 
-func (alwaysAdmitController) AdmissionControl(operation, kind, namespace string, object runtime.Object) (err error) {
-	return nil
+func (ac *stubAdmissionController) AdmissionControl(operation, kind, namespace string, object runtime.Object) (err error) {
+	if !ac.admit {
+		err = errors.New("No changes allowed")
+	}
+	return err
 }
 
 func NewAlwaysAdmitController() AdmissionControl {
-	return new(alwaysAdmitController)
+	return &stubAdmissionController{
+		admit: true,
+	}
+}
+
+func NewAlwaysDenyController() AdmissionControl {
+	return &stubAdmissionController{
+		admit: false,
+	}
 }
 
 type admissionController struct {