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: api_integration_test.go
    path of file: ./repos/vault/vault/external_tests/api
    
    the code of the file until where you have to start completion: // Copyright (c) HashiCorp, Inc.
// SPDX-License-Identifier: BUSL-1.1

package api

import (
	"encoding/base64"
	"testing"

	"github.com/hashicorp/vault/api"
	"github.com/hashicorp/vault/audit"
	auditFile "github.com/hashicorp/vault/builtin/audit/file"
	credUserpass "github.com/hashico
    
func testVaultServerCoreConfig(t testing.TB, coreConfig *vault.CoreConfig) (*api.Client, []string, func()) {
	t.Helper()

	cluster := vault.NewTestCluster(benchhelpers.TBtoT(t), coreConfig, &vault.TestClusterOptions{
		HandlerFunc: http.Handler,
		NumCores:    1,
	})
	cluster.Start()

	// Make it easy to get access to the active
	core := cluster.Cores[0].Core
	vault.TestWaitActive(benchhelpers.TBtoT(t), core)

	// Get the client already setup for us!
	client := cluster.Cores[0].Client
	client.SetToken(cluster.RootToken)

	// Convert the unseal keys to base64 encoded, since these are how the user
	// will get them.
	unsealKeys := make([]string, len(cluster.BarrierKeys))
	for i := range unsealKeys {
		unsealKeys[i] = base64.StdEncoding.EncodeToString(cluster.BarrierKeys[i])
	}

	return client, unsealKeys, func() { defer cluster.Cleanup() }
}