test: add unit test for UseLocationHost fix in HandlerWithErrorResponder

Author: udayakp

pkg/server/handler/handler_test.go

@@ -16,14 +16,7 @@ func (f *fakeResponder) Error(w http.ResponseWriter, _ *http.Request, err error)
 	http.Error(w, err.Error(), http.StatusInternalServerError)
 }
 
-// TestHandlerWithErrorResponder_UseLocationHost verifies that UseLocationHost=true causes
-// the UpgradeAwareHandler to send the backend hostname as the Host header, not the
-// original client Host header.
-//
-// On clusters where the API server is fronted by an Istio proxy (e.g. Gardener shoots),
-// Istio enforces virtual host routing and returns 404 for any Host value it does not
-// recognise. Without this fix, kubectl logs/exec/port-forward fail because the handler
-// forwards the vcluster LB hostname instead of the actual API server hostname.
+// TestHandlerWithErrorResponder_UseLocationHost verifies that the backend receives the correct Host header, not the client's vcluster LB hostname.
 func TestHandlerWithErrorResponder_UseLocationHost(t *testing.T) {
 	var receivedHost string
 	backend := httptest.NewTLSServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
@@ -43,7 +36,7 @@ func TestHandlerWithErrorResponder_UseLocationHost(t *testing.T) {
 	// Simulate a client request with a vcluster LB hostname as Host —
 	// this is what the UpgradeAwareHandler used to forward before the fix.
 	req := httptest.NewRequest(http.MethodGet, "/api/v1/namespaces/default/pods/test/log", nil)
-	req.Host = "vcluster-lb.us-west-2.elb.amazonaws.com"
+	req.Host = "vcluster.example.com"
 
 	h.ServeHTTP(httptest.NewRecorder(), req)