Laraval - Model Fields Is Returning Null

I have a weird issue that is causing my unit tests to fail in Laravel. I have a table that is created like this:

Schema::create('message_threads', function (Blueprint $table) {
            $table->string('id')->primary();
            $table->timestamps();
            $table->softDeletes();
            $table->string('user_id');
            $table->string('folder_id')->nullable();
            $table->boolean('starred')->default(false);
            $table->string('thread_id')->nullable();
            $table->foreign('user_id')->references('id')->on('users');
            $table->foreign('folder_id')->references('id')->on('message_folders')->onDelete('cascade');
        });

And in its associated model, when I call the getAttributes() function, the fields starred and folder_id are not present.

//The code
$messageThread = factory(MessageThread::class)->create();
print_r($messageThread->getAttributes());

Outputs the followings:

(
    [user_id] => USR-258995103d8c4d37bd6ec3a38dfe9312
    [id] => MTD-cb4f8f66ddfc4385b31155212cb57f91
    [updated_at] => 2020-02-27 14:15:55
    [created_at] => 2020-02-27 14:15:55
)

Why are these fields missing, especially the starred field, which has a default value of false?

via Chebli Mohamed