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: iam_spanner_instance_test.go
    path of file: ./repos/magic-modules/mmv1/third_party/terraform/services/spanner
    
    the code of the file until where you have to start completion: package spanner_test

import (
	"fmt"
	"testing"

	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/resource"
	"github.com/hashicorp/terraform-provider-google/google/acctest"
	"github.com/hashicorp/terraform-provider-google/google/env
    
func testAccSpannerInstanceIamBinding_basic(account, instance, roleId string) string {
	return fmt.Sprintf(`
resource "google_service_account" "test_account" {
  account_id   = "%s"
  display_name = "Spanner Instance Iam Testing Account"
}

resource "google_spanner_instance" "instance" {
  name         = "%s"
  config       = "regional-us-central1"
  display_name = "%s"
  num_nodes    = 1
}

resource "google_spanner_instance_iam_binding" "foo" {
  project  = google_spanner_instance.instance.project
  instance = google_spanner_instance.instance.name
  role     = "%s"
  members  = ["serviceAccount:${google_service_account.test_account.email}"]
}
`, account, instance, instance, roleId)
}