Laravel 5.7 Unable to locate factory with name [default] [App\User]

The error is also thrown due to importing the wrong TestCase and not just parent::setUp(); only

-

use PHPUnit\Framework\TestCase; [WRONG: and throws this error]

---

use Tests\TestCase; [CORRECT]

Ohh shoot! parent::setUp() fixed this issue.

public function setUp()
{
    parent::setUp();

    // more codes here
}