@tzookb if you're asking how to set the header when you do a post request in your test, then you can do the following (assuming you're using Laravel 5.1):
$this->post('blogs', ['title' => 'awesome blog post'], ['HTTP_Authorization' => 'Bearer' . $token]);
So in the third argument you can pass your headers. The same goes for the put, patch and delete methods. The get method takes the headers as a second argument as there is no post data.
If you want the headers to be accessible by $request->headers(), then you have to prefix it with HTTP_.
If you're not using Laravel 5.1 then you can use the call method which takes the header data as the 6th argument, below you can see the public interface of the method.
/**
* Call the given URI and return the Response.
*
* @param string $method
* @param string $uri
* @param array $parameters
* @param array $cookies
* @param array $files
* @param array $server
* @param string $content
* @return \Illuminate\Http\Response
*/
public function call($method, $uri, $parameters = [], $cookies = [], $files = [], $server = [], $content = null)