public function testUnique()
{
for ($i = 0; $i < 20; $i++) {
$post = Post::create(['title' => 'A post title']);
if ($i == 0) {
$this->assertEquals('a-post-title', $post->slug);
} else {
$this->assertEquals('a-post-title-' . $i, $post->slug);
}
}
}