Add more tests and clear the values

Code Coverage Report:      
  2020-11-02 17:00:32      
                           
 Summary:                  
  Classes: 80.00% (4/5)    
  Methods: 86.67% (26/30)  
  Lines:   86.98% (167/192)

Samyoul\U2F\U2FServer\Registration
  Methods: 100.00% ( 7/ 7)   Lines: 100.00% ( 10/ 10)
Samyoul\U2F\U2FServer\RegistrationRequest
  Methods: 100.00% ( 5/ 5)   Lines: 100.00% (  9/  9)
Samyoul\U2F\U2FServer\SignRequest
  Methods: 100.00% ( 6/ 6)   Lines: 100.00% ( 12/ 12)
Samyoul\U2F\U2FServer\U2FException
  Methods: 100.00% ( 1/ 1)   Lines: 100.00% (  2/  2)
Samyoul\U2F\U2FServer\U2FServer
  Methods:  63.64% ( 7/11)   Lines:  84.28% (134/159)

Author: williamdes

src/U2FServer.php

@@ -84,9 +84,7 @@ public static function makeRegistration($appId, array $registrations = [])
     public static function register(RegistrationRequest $request, $response, $attestDir = null, $includeCert = true)
     {
         // Parameter Checks
-        if( !is_object( $request ) ) {
-            throw new \InvalidArgumentException('$request of register() method only accepts object.');
-        }
+        // $request is safe because of the php typehint
 
         if( !is_object( $response ) ) {
             throw new \InvalidArgumentException('$response of register() method only accepts object.');