Laravel-excel: [BUG] Error import: object beginTransaction

Prerequisites

• [x] Able to reproduce the behaviour outside of your code, the problem is isolated to Laravel Excel.
• [x] Checked that your issue isn't already filed.
• [x] Checked if no PR was submitted that fixes this problem.

Versions

• PHP version: 7.2
• Laravel version: 5.7.17
• Package version: 3.1.3

Description

I have created the import object class and specified the Concerns of ToCollection. Upon performing Excel::import, I receive an error shown in Actual Behavior below.

Steps to Reproduce

Do not use a transactional database. We use MongoDB.

Aside from that, Model importing was not specified and the package should not be doing any database preparation, that should be handled through events by the developer.

Expected behavior:

dd of the collection rows.

Actual behavior:

1) Tests\Unit\Services\Websites\WebsiteCredentialsImportServiceTest::testImportTabDelimited
Error: Call to a member function beginTransaction() on null

/var/www/vhosts/website.local/vendor/laravel/framework/src/Illuminate/Database/Concerns/ManagesTransactions.php:109
/var/www/vhosts/website.local/vendor/laravel/framework/src/Illuminate/Database/Concerns/ManagesTransactions.php:93
/var/www/vhosts/website.local/vendor/laravel/framework/src/Illuminate/Database/Concerns/ManagesTransactions.php:23
/var/www/vhosts/website.local/vendor/laravel/framework/src/Illuminate/Database/DatabaseManager.php:327
/var/www/vhosts/website.local/vendor/laravel/framework/src/Illuminate/Support/Facades/Facade.php:223
/var/www/vhosts/website.local/vendor/maatwebsite/excel/src/Reader.php:96
/var/www/vhosts/website.local/vendor/maatwebsite/excel/src/Excel.php:120
/var/www/vhosts/website.local/vendor/laravel/framework/src/Illuminate/Support/Facades/Facade.php:223
/var/www/vhosts/website.local/app/Services/Websites/WebsiteCredentialsImportService.php:198
/var/www/vhosts/website.local/app/Services/Websites/WebsiteCredentialsImportService.php:182
/var/www/vhosts/website.local/app/Services/Websites/WebsiteCredentialsImportService.php:122
/var/www/vhosts/website.local/tests/Unit/Services/Websites/WebsiteCredentialsImportServiceTest.php:25

Additional Information

<?php

namespace App\Imports\Websites;

use Illuminate\Support\Collection;
use Maatwebsite\Excel\Concerns\ToCollection;

/**
 * Class WebsiteCredentialsImport
 *
 * @package App\Imports\Websites
 */
class WebsiteCredentialsImport implements ToCollection
{
    public function collection(Collection $rows)
    {
        dd(['COLLECTION' => $rows]);
    }
}

        $collection = Excel::import(
            new WebsiteCredentialsImport,
            $this->file_name,
            null,
            $this->reader_type
        );