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: service_test.go
    path of file: ./repos/magistrala/auth
    
    the code of the file until where you have to start completion: // Copyright (c) Abstract Machines
// SPDX-License-Identifier: Apache-2.0

package auth_test

import (
	"context"
	"fmt"
	"testing"
	"time"

	"github.com/absmach/magistrala/auth"
	"github.com/absmach/magistrala/auth/jwt"
	"github.com/absmach/magistrala/auth/mocks"
	"github.com/absmach/magistrala/pkg/errors"
	repoerr "github.com/absmach/magistrala/pkg/errors/repository"
	svcerr "github.com/absmach/magistrala/pkg/errors/service"
	oauth2mocks "github.com/absmach/magistrala/pkg/oauth2/mocks"
	"github.com/absmach/magistrala/pkg/uuid"
	"github
    
func TestDecodeDomainUserID(t *testing.T) {
	cases := []struct {
		desc         string
		domainUserID string
		respDomainID string
		respUserID   string
	}{
		{
			desc:         "decode domain user id successfully",
			domainUserID: validID + "_" + validID,
			respDomainID: validID,
			respUserID:   validID,
		},
		{
			desc:         "decode domain user id with empty domainUserID",
			domainUserID: "",
			respDomainID: "",
			respUserID:   "",
		},
		{
			desc:         "decode domain user id with empty UserID",
			domainUserID: validID,
			respDomainID: validID,
			respUserID:   "",
		},
		{
			desc:         "decode domain user id with invalid domainuserId",
			domainUserID: validID + "_" + validID + "_" + validID + "_" + validID,
			respDomainID: "",
			respUserID:   "",
		},
	}

	for _, tc := range cases {
		ar, er := auth.DecodeDomainUserID(tc.domainUserID)
		assert.Equal(t, tc.respUserID, er, fmt.Sprintf("%s expected %s got %s\n", tc.desc, tc.respUserID, er))
		assert.Equal(t, tc.respDomainID, ar, fmt.Sprintf("%s expected %s got %s\n", tc.desc, tc.respDomainID, ar))
	}
}