add a fuzz function for expapi.APIVersion

pkg/api/testing/fuzzer.go

@@ -26,6 +26,7 @@ import (
 	"k8s.io/kubernetes/pkg/api"
 	"k8s.io/kubernetes/pkg/api/registered"
 	"k8s.io/kubernetes/pkg/api/resource"
+	"k8s.io/kubernetes/pkg/expapi"
 	"k8s.io/kubernetes/pkg/fields"
 	"k8s.io/kubernetes/pkg/labels"
 	"k8s.io/kubernetes/pkg/runtime"
@@ -301,6 +302,11 @@ func FuzzerFor(t *testing.T, version string, src rand.Source) *fuzz.Fuzzer {
 			c.FuzzNoCustom(n)
 			n.Spec.ExternalID = "external"
 		},
+		func(s *expapi.APIVersion, c fuzz.Continue) {
+			// We can't use c.RandString() here because it may generate empty
+			// string, which will cause tests failure.
+			s.APIGroup = "something"
+		},
 	)
 	return f
 }