Error 500 when exectuting basic phpunit test on laravel

I have a Laravel application running on my local network with Vagrant Homestead. I tries to implement HTTP tests and I started by creating a basic test like the documentation :

/**
 * A basic feature test example.
 *
 * @return void
 */
public function testExample()
{
    $response = $this->get('/');

    $response->assertStatus(200);
}

But when I run the test I receive the error : Expected status code 200 but received 500.

However I can acces my site without any issues.

What I am doing wrong ?

Thanks