Laravel Test Case custom headers doesn't found in RouteServiceProvider

Hi, I have multiple API versions and each version have a dedicated route file, whenever API is called with a client it provides a specific API version in headers which is being retrieved in RouteServiceProvider. The problem is that when I am performing a test the request doesn't have the custom headers which I am providing with the JSON call.

Below is the test case code.

   $response = $this->postJson('/api/user/team/1/slideshow', [
            'topic' => 'test topic',
            'content' => 'test content',
            'media' => 'test media',
        ], [
            'Accept-Version' => 1.3,
            'Authorization' => 'Bearer '.'asdfasdfasdf',
            'Content-Type' => 'application/json',
            'Accept' => 'application/json'
        ]);

        $response->assertStatus(200);

and this is RouteServiceProvider code

  Route::prefix('api')
            ->middleware('api')
            ->namespace($this->apiNamespace)
            ->group(function(){

                $apiVersion = Request::header('Accept-version');

                if($apiVersion){ // if the api version is set

                    $minApiVersion = config('app.min_api_verion_support');

                    if($minApiVersion > $apiVersion){ // check if api version is obsoleted
                        throw APIVersion::obsoleted($apiVersion);
                    }
                    
                    Request::merge(['api_version' => $apiVersion]); // set api version to request object
    
                    $apiVersionNamespace = 'v' . str_replace('.','_',$apiVersion); // generate api version namespace

                    Route::namespace($apiVersionNamespace)->group(base_path("routes/api_v{$apiVersion}.php"));
                }else{ // if api version is not set then use the default api version
                    Route::namespace('')->group(base_path("routes/api.php"));
                }
            });

I would like also add there, as there is no Accept-Version find in request headers so it reads the default api.php file. and there is a surpizing output when i write this code here.

dump(request()->headers);    

Route::post('/user/team/1/slideshow', function(){
    dump(request()->headers);    
    return 'request handled';
});

In the output when dump function is called without route it shows different headers and in Route callback there are different headers

Symfony\Component\HttpFoundation\HeaderBag^ {#347
  #headers: array:5 [
    "host" => array:1 [
      0 => "demo.test"
    ]
    "user-agent" => array:1 [
      0 => "Symfony"
    ]
    "accept" => array:1 [
      0 => "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8"
    ]
    "accept-language" => array:1 [
      0 => "en-us,en;q=0.5"
    ]
    "accept-charset" => array:1 [
      0 => "ISO-8859-1,utf-8;q=0.7,*;q=0.7"
    ]
  ]
  #cacheControl: []
}
Symfony\Component\HttpFoundation\HeaderBag^ {#818
  #headers: array:9 [
    "host" => array:1 [
      0 => "demo.test"
    ]
    "user-agent" => array:1 [
      0 => "Symfony"
    ]
    "accept" => array:1 [
      0 => "application/json"
    ]
    "accept-language" => array:1 [
      0 => "en-us,en;q=0.5"
    ]
    "accept-charset" => array:1 [
      0 => "ISO-8859-1,utf-8;q=0.7,*;q=0.7"
    ]
    "content-length" => array:1 [
      0 => 88
    ]
    "content-type" => array:1 [
      0 => "application/json"
    ]
    "accept-version" => array:1 [
      0 => 1.3
    ]
    "authorization" => array:1 [
      0 => "Bearer asdfasdfasdf"
    ]
  ]
  #cacheControl: []
}