change rbac roleref type

pkg/api/testing/fuzzer.go

@@ -30,6 +30,7 @@ import (
 	"k8s.io/kubernetes/pkg/apis/autoscaling"
 	"k8s.io/kubernetes/pkg/apis/batch"
 	"k8s.io/kubernetes/pkg/apis/extensions"
+	"k8s.io/kubernetes/pkg/apis/rbac"
 	"k8s.io/kubernetes/pkg/fields"
 	"k8s.io/kubernetes/pkg/labels"
 	"k8s.io/kubernetes/pkg/runtime"
@@ -498,6 +499,14 @@ func FuzzerFor(t *testing.T, version unversioned.GroupVersion, src rand.Source)
 				}
 			}
 		},
+		func(r *rbac.RoleRef, c fuzz.Continue) {
+			c.FuzzNoCustom(r) // fuzz self without calling this function again
+
+			// match defaulter
+			if len(r.APIGroup) == 0 {
+				r.APIGroup = rbac.GroupName
+			}
+		},
 		func(r *runtime.RawExtension, c fuzz.Continue) {
 			// Pick an arbitrary type and fuzz it
 			types := []runtime.Object{&api.Pod{}, &extensions.Deployment{}, &api.Service{}}