what is this testing?

The test was unnecessary as there was no operational logic in the code being tested, so I removed it

should this test that this has something in Status and is cleared?

Should some cleaning logic be added to the method being tested?

// PrepareForCreate clears the status of an ServiceCIDR before creation.
func (serviceCIDRStrategy) PrepareForCreate(ctx context.Context, obj runtime.Object) {
	_ = obj.(*networking.ServiceCIDR)

}

yep

I prefer the existing mode in other places that does not depend on the api group and version

func TestStrategy_ResetFields(t *testing.T) {
	resetFields := Strategy.GetResetFields()
	if len(resetFields) != 1 {
		t.Errorf("ResetFields should have 1 element, but have %d", len(resetFields))
	}
}

Yes , it's better.

is this not an error?

No?

it should be, the newObj contains an invalud cidr 🤔

it should be, the newObj contains an invalud cidr 🤔

The assertion fails if the length of error is zero in this test. This is as expected

oh, lol ... then assert on the exact number of errors

Yes

this is still missing, I think it should be something as

if len(errors) != 1 { 
  t.Errorf("Expected 1 validation errors for invalid update, got %d", len(errors))

Making precise assertions is not easy to achieve.
If the test code is

oldObj := newServiceCIDR()
newObj := oldObj.DeepCopy()
newObj.Spec.CIDRs = []string{"bad cidr"}
if len(errors) != 1 {
	t.Errorf("Expected 1 validation errors for invalid update, got %d, errors: %v", len(errors), errors)
}

it got a log as

=== RUN   TestServiceCIDRStrategy
    /root/go/src/k8s.io/kubernetes/pkg/registry/networking/servicecidr/strategy_test.go:62: Expected 1 validation errors for invalid update, got 2, errors: [spec.cidrs[0]: Invalid value: "bad cidr": netip.ParsePrefix("bad cidr"): no '/' spec.cidrs: Invalid value: []string{"bad cidr"}: field is immutable]
--- FAIL: TestServiceCIDRStrategy (0.00s)
FAIL
FAIL    k8s.io/kubernetes/pkg/registry/networking/servicecidr   0.055s

ok, then 2 errors are expected , you can create a table test here if you want or just use

if len(errors) != 2 { 
  t.Errorf("Expected 2 validation errors for invalid update, got %d", len(errors))

Done

same comment as before, assert on the exact number of errors we are expecting

Done, thank you very much.

you have a mismatch, or either 1 or 2 :)

oh, I'm sorry, it's done now, thank you very much