Error: Class "App\Common\PrintLoggerTool" not found

Question

I am new to PHP, and I am going to add some unit test for existed code app\Common\PrintLoggerTool.php.

<?php

/**
 * Created by PhpStorm.
 * User: tong
 * Date: 2021/1/8
 * Time: 9:46
 */

namespace App\Common;

class PrintLoggerTool
{
    public static function printLogger(string $method, $getMessage, $level = 1)
    {
        // Just some code of log, ignored.
    }
}

Below is my test code, test\Cases\Common\PrintLoggerToolTest.php

<?php

declare(strict_types=1);
/**
 * This file is part of Hyperf.
 *
 * @link     https://www.hyperf.io
 * @document https://hyperf.wiki
 * @contact  [email protected]
 * @license  https://github.com/hyperf/hyperf/blob/master/LICENSE
 */

namespace HyperfTest\Cases\Common;

use App\Common\PrintLoggerTool;
use PHPUnit\Framework\TestCase;

/**
 * @internal
 * @coversNothing
 */
class PrintLoggerToolTest extends TestCase
{
    public function testDecrypt()
    {
        PrintLoggerTool::printLogger(__METHOD__, 'abc', 2);
    }
}

But when I run the test code, I got:Error: Class "App\Common\PrintLoggerTool" not found. And I can not run existed unit test either, for same error.

So I think there may be some "environment problem" on my computer.

I find something in composer.json

{
    "autoload": {
        "psr-4": {
            "App\\": "app/"
        },
        "files": []
    },
    "autoload-dev": {
        "psr-4": {
            "HyperfTest\\": "./test/"
        }
    }
    // other code ingored
}

So I think the "namespace" I use is right.