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: flashback_test.go
    path of file: ./repos/tidb/tests/realtikvtest/flashbacktest
    
    the code of the file until where you have to start completion: // Copyright 2022 PingCAP, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distribute
    
func MockGC(tk *testkit.TestKit) (string, string, string, func()) {
	originGC := ddlutil.IsEmulatorGCEnable()
	resetGC := func() {
		if originGC {
			ddlutil.EmulatorGCEnable()
		} else {
			ddlutil.EmulatorGCDisable()
		}
	}

	// disable emulator GC.
	// Otherwise emulator GC will delete table record as soon as possible after execute drop table ddl.
	ddlutil.EmulatorGCDisable()
	timeBeforeDrop := time.Now().Add(0 - 48*60*60*time.Second).Format(tikvutil.GCTimeFormat)
	timeAfterDrop := time.Now().Add(48 * 60 * 60 * time.Second).Format(tikvutil.GCTimeFormat)
	safePointSQL := `INSERT HIGH_PRIORITY INTO mysql.tidb VALUES ('tikv_gc_safe_point', '%[1]s', '')
			       ON DUPLICATE KEY
			       UPDATE variable_value = '%[1]s'`
	// clear GC variables first.
	tk.MustExec("delete from mysql.tidb where variable_name in ( 'tikv_gc_safe_point','tikv_gc_enable' )")
	return timeBeforeDrop, timeAfterDrop, safePointSQL, resetGC
}