In response to this:

What type of PR is this?

/kind test
/area conformance-test

What this PR does / why we need it:

A conformance test to verify that the gateway correctly reports the endpoint that served the request.

verified with GKE

go test -v ./conformance -args -debug -gateway-class gke-l7-regional-external-managed -cleanup-base-resources=false -allow-crds-mismatch=true -run-test GatewayDestinationEndpointServed

Result:

   roundtripper.go:262: 2025-11-13T19:18:07.43605216Z: Received Response:
       < HTTP/1.1 200 OK
       < Connection: close
       < Transfer-Encoding: chunked
       < Content-Type: application/json
       < Date: Thu, 13 Nov 2025 19:18:07 GMT
       < Via: 1.1 google
       < X-Conformance-Test-Served-Endpoint: 10.116.13.18:3000
       < X-Content-Type-Options: nosniff
       < X-Went-Into-Resp-Headers: true
       < 
       < 261
       < {"headers":{"Accept-Encoding":["gzip"],"Test-Epp-Endpoint-Selection":["10.116.13.18"],"User-Agent":["Go-http-client/1.1"],"Via":["1.1 google"],"X-Echo-Set-Header":[""],"X-Forwarded-For":["34.170.214.239,35.212.149.233"],"X-Forwarded-Proto":["http"],"X-Gateway-Destination-Endpoint":["10.116.13.18:3000"],"X-Request-Id":["10d53a31-1740-448b-972c-a7dcfdf33276"]},"host":"primary.example.com","ingress":"","method":"POST","namespace":"inference-conformance-app-backend","path":"/destination-endpoint-served-test","pod":"primary-inference-model-server-deployment-845888f54f-hcblv","proto":"HTTP/1.1","service":""}
       < 0
       < 
       < 
       
       
   http.go:282: 2025-11-13T19:18:07.436225548Z: Request passed
=== NAME  TestConformance/GatewayDestinationEndpointServed
   apply.go:283: 2025-11-13T19:18:07.436304048Z: Deleting httproute-for-destination-endpoint-served HTTPRoute
=== RUN   TestConformance/GatewayFollowingEPPRouting
   conformance.go:66: Skipping GatewayFollowingEPPRouting: test explicitly skipped
=== RUN   TestConformance/GatewayWeightedAcrossTwoInferencePools
   conformance.go:66: Skipping GatewayWeightedAcrossTwoInferencePools: test explicitly skipped
=== RUN   TestConformance/HTTPRouteInvalidInferencePoolRef
   conformance.go:66: Skipping HTTPRouteInvalidInferencePoolRef: test explicitly skipped
=== RUN   TestConformance/HTTPRouteMultipleGatewaysDifferentPools
   conformance.go:66: Skipping HTTPRouteMultipleGatewaysDifferentPools: test explicitly skipped
=== RUN   TestConformance/InferencePoolAccepted
   conformance.go:66: Skipping InferencePoolAccepted: test explicitly skipped
=== RUN   TestConformance/InferencePoolHTTPRoutePortValidation
   conformance.go:66: Skipping InferencePoolHTTPRoutePortValidation: test explicitly skipped
=== RUN   TestConformance/InferencePoolInvalidEPPService
   conformance.go:66: Skipping InferencePoolInvalidEPPService: test explicitly skipped
=== RUN   TestConformance/HTTPRouteMultipleRulesDifferentPools
   conformance.go:66: Skipping HTTPRouteMultipleRulesDifferentPools: test explicitly skipped
=== RUN   TestConformance/InferencePoolResolvedRefsCondition
   conformance.go:66: Skipping InferencePoolResolvedRefsCondition: test explicitly skipped
--- PASS: TestConformance (110.64s)
   --- SKIP: TestConformance/EppUnAvailableFailOpen (0.00s)
   --- PASS: TestConformance/GatewayDestinationEndpointServed (107.07s)
       --- PASS: TestConformance/GatewayDestinationEndpointServed/Request_is_served_by_the_selected_backend_pod (79.48s)
   --- SKIP: TestConformance/GatewayFollowingEPPRouting (0.00s)
   --- SKIP: TestConformance/GatewayWeightedAcrossTwoInferencePools (0.00s)
   --- SKIP: TestConformance/HTTPRouteInvalidInferencePoolRef (0.00s)
   --- SKIP: TestConformance/HTTPRouteMultipleGatewaysDifferentPools (0.00s)
   --- SKIP: TestConformance/InferencePoolAccepted (0.00s)
   --- SKIP: TestConformance/InferencePoolHTTPRoutePortValidation (0.00s)
   --- SKIP: TestConformance/InferencePoolInvalidEPPService (0.00s)
   --- SKIP: TestConformance/HTTPRouteMultipleRulesDifferentPools (0.00s)
   --- SKIP: TestConformance/InferencePoolResolvedRefsCondition (0.00s)
PASS
ok  	sigs.k8s.io/gateway-api-inference-extension/conformance	110.864s

Which issue(s) this PR fixes:

Fixes #1670

Does this PR introduce a user-facing change?:

New conformance test to verify: https://github.com/kubernetes-sigs/gateway-api-inference-extension/tree/main/docs/proposals/004-endpoint-picker-protocol#destination-endpoint-served

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-sigs/prow repository.

• OWNERS [kfswain]

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