How to append key value to the result of factory()->make() in Laravel?

I am writting a Test Case.

Lets say there is a Threads model with fields: user_id, title, body

So to test wheather submitting the Thread works, I am doing this:

$user = factory('App\User')->create();
$thread = factory('App\Thread')->make(['user_id' => $user->id]);
$this->post('/threads', $thread->toArray());

$this->get('/thread/'.$thread->id)
            ->assertSee($thread->title)

But I have yet another field that I want to post along with the thread which is not part of the thread model.

eg.

community => 'some_community'

So how do I append another field before posting the array to /threads.

How can I append key value pair to the result of make() ???

via Chebli Mohamed