You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: balancer_conn_wrappers_test.go
    path of file: ./repos/sharingan/grpc-server/v1.33.2
    
    the code of the file until where you have to start completion: /*
 *
 * Copyright 2019 gRPC authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file exce
    
func (s) TestRoundRobinZeroAddressesResolverPolling(t *testing.T) {
	// We need to start a real server or else the connecting loop will call
	// ResolveNow after every iteration, even after a valid resolver result is
	// returned.
	lis, err := net.Listen("tcp", "localhost:0")
	if err != nil {
		t.Fatalf("Error while listening. Err: %v", err)
	}
	defer lis.Close()
	s := NewServer()
	defer s.Stop()
	go s.Serve(lis)

	testResolverErrorPolling(t,
		func(r *manual.Resolver) {
			// No addresses so the balancer will fail.
			r.CC.UpdateState(resolver.State{})
		}, func(r *manual.Resolver) {
			// UpdateState will block if ResolveNow is being called (which
			// blocks on rn), so call it in a goroutine.  Include a valid
			// address so the balancer will be happy.
			go r.CC.UpdateState(resolver.State{Addresses: []resolver.Address{{Addr: lis.Addr().String()}}})
		},
		WithDefaultServiceConfig(fmt.Sprintf(`{ "loadBalancingConfig": [{"%v": {}}] }`, roundrobin.Name)))
}