Cannot use client-go's fake client with Gateway API objects

[pmalek]

What happened?

I'm trying to work with Gateway API fake objects by doing the following:

package x

import (
	"testing"

	"github.com/stretchr/testify/require"
	"k8s.io/client-go/kubernetes/fake"
	clientsetscheme "k8s.io/client-go/kubernetes/scheme"
	gatewayv1beta1 "sigs.k8s.io/gateway-api/apis/v1beta1"
	gatewayscheme "sigs.k8s.io/gateway-api/pkg/client/clientset/versioned/scheme"
)

func TestGatewayFake(t *testing.T) {
	require.NoError(t, gatewayscheme.AddToScheme(clientsetscheme.Scheme))

	_ = fake.NewSimpleClientset(&gatewayv1beta1.Gateway{})
}

but that doesn't work, i.e. I get this:

panic: no kind is registered for the type v1beta1.Gateway in scheme "pkg/runtime/scheme.go:100" [recovered]
        panic: no kind is registered for the type v1beta1.Gateway in scheme "pkg/runtime/scheme.go:100"

What would work is

package x

import (
	"testing"

	"github.com/stretchr/testify/require"
	"k8s.io/client-go/kubernetes/fake"
	gatewayv1beta1 "sigs.k8s.io/gateway-api/apis/v1beta1"
	gatewayscheme "sigs.k8s.io/gateway-api/pkg/client/clientset/versioned/scheme"
)

func TestGatewayFake(t *testing.T) {
	require.NoError(t, gatewayscheme.AddToScheme(fake.Scheme)) // <- this is not possible currently.

	_ = fake.NewSimpleClientset(&gatewayv1beta1.Gateway{})
}

with the twist that the Scheme in client-go's fake package gets exported.

I was suggested to create an issue in this repo as client-go might get overlooked and not triaged.

Related #sig-api-machinery thread: https://kubernetes.slack.com/archives/C0EG7JC6T/p1676125039126589

What did you expect to happen?

Fake object to work with client-go

How can we reproduce it (as minimally and precisely as possible)?

package x

import (
	"testing"

	"github.com/stretchr/testify/require"
	"k8s.io/client-go/kubernetes/fake"
	clientsetscheme "k8s.io/client-go/kubernetes/scheme"
	gatewayv1beta1 "sigs.k8s.io/gateway-api/apis/v1beta1"
	gatewayscheme "sigs.k8s.io/gateway-api/pkg/client/clientset/versioned/scheme"
)

func TestGatewayFake(t *testing.T) {
	require.NoError(t, gatewayscheme.AddToScheme(clientsetscheme.Scheme))

	_ = fake.NewSimpleClientset(&gatewayv1beta1.Gateway{})
}

Anything else we need to know?

No response

Kubernetes version

N/A

Cloud provider

N/A

OS version

# On Linux:
$ cat /etc/os-release
# paste output here
$ uname -a
# paste output here

# On Windows:
C:\> wmic os get Caption, Version, BuildNumber, OSArchitecture
# paste output here

Install tools

Container runtime (CRI) and version (if applicable)

Related plugins (CNI, CSI, ...) and versions (if applicable)

No response

[pmalek]

/sig api-machinery

[cici37]

/sig network

[aojea]

/cc @shaneutt @robscott

[robscott]

Hey @pmalek, you also need to find a way to add the Gateway API types to the scheme first, something like this:

https://github.com/kubernetes-sigs/gateway-api/blob/aa35a96894895b52911ea0ece00b49717be55b7e/conformance/conformance_test.go#L45-L46.

Feel free to follow up on Gateway API Slack if you're still running into issues, lots of people there that would have dealt with this.

/close

[k8s-ci-robot]

@robscott: Closing this issue.

In response to this:

Hey @pmalek, you also need to find a way to add the Gateway API types to the scheme first, something like this:

https://github.com/kubernetes-sigs/gateway-api/blob/aa35a96894895b52911ea0ece00b49717be55b7e/conformance/conformance_test.go#L45-L46.

Feel free to follow up on Gateway API Slack if you're still running into issues, lots of people there that would have dealt with this.

/close

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[robscott]

Actually, looks like I misread the issue, would still recommend chatting in #sig-network-gateway-api on Slack, but reopening because I don't think my suggested solution was helpful.

/reopen

[k8s-ci-robot]

@robscott: Reopened this issue.

In response to this:

Actually, looks like I misread the issue, would still recommend chatting in #sig-network-gateway-api on Slack, but reopening because I don't think my suggested solution was helpful.

/reopen

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[MikeZappa87]

/assign @shaneutt

[lavalamp]

For clarity, the request here is to export fake's schema so that other objects can be added to it, or for the ability to pass a schema in for fakes to use.

[pmalek]

For clarity, the request here is to export fake's schema so that other objects can be added to it, or for the ability to pass a schema in for fakes to use.

Yes. Either that or explain/document a way to do it differently.

[cici37]

/triage accepted

[lavalamp]

Yeah, I don't think there's going to be any other options.

/assign @apelisse

[shaneutt]

As we discussed in slack this is not networking specific, thanks @lavalamp! 👍

/remove-sig network

[arbreezy]

is there any workaround or a different approach maybe ?

[pmalek]

is there any workaround or a different approach maybe ?

Unfortunately not for the k8s.io/client-go/kubernetes/fake but for gateway-api's fake client (sigs.k8s.io/gateway-api/pkg/client/clientset/versioned/fake) it does seem to (kinda) work:

package main

import (
	"testing"

	gatewayv1 "sigs.k8s.io/gateway-api/apis/v1"
	gatewaysfake "sigs.k8s.io/gateway-api/pkg/client/clientset/versioned/fake"
)

func TestGatewayFakeClient(t *testing.T) {
	k8sclient := gatewaysfake.NewSimpleClientset(&gatewayv1.Gateway{})
	_ = k8sclient
}

So you can get a working client but unfortunately due to kubernetes/client-go#1082 you won't get it work work:

package main

import (
	"context"
	"testing"

	"github.com/stretchr/testify/require"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	gatewayv1 "sigs.k8s.io/gateway-api/apis/v1"
	gatewaysfake "sigs.k8s.io/gateway-api/pkg/client/clientset/versioned/fake"
)

func TestGatewayFakeClientGet(t *testing.T) {
	ctx := context.Background()
	gw := &gatewayv1.Gateway{
		ObjectMeta: metav1.ObjectMeta{
			Name:      "gw",
			Namespace: "default",
		},
	}
	k8sclient := gatewaysfake.NewSimpleClientset(gw)
	gatewaysClient := k8sclient.GatewayV1().Gateways("default")
	gw, err := gatewaysClient.Get(ctx, "gw", metav1.GetOptions{})
	require.NoError(t, err)
}

        	Error:      	Received unexpected error:
        	            	gateways.gateway.networking.k8s.io "gw" not found
        	Test:       	TestGatewayFakeClientGet

This is due to https://github.com/kubernetes/client-go/blob/84a6fe7e4032ae1b8bc03b5208e771c5f7103549/testing/fixture.go#L292 holding gatewaies not gateways:

[miguelvr]

I just bumped into this. Is it currently impossible to use a fake client with Gateway resources?