add use at top and use assertNull

src/Routing/Router.php

@@ -17,6 +17,7 @@ namespace Cake\Routing;
 use Cake\Core\Configure;
 use Cake\Http\ServerRequest;
 use Cake\Utility\Inflector;
+use Cake\Routing\Exception\MissingRouteException;
 use Psr\Http\Message\ServerRequestInterface;
 
 /**
@@ -725,7 +726,7 @@ class Router
     {
         try {
             return static::url($url, $full);
-        } catch (\Cake\Routing\Exception\MissingRouteException $e) {
+        } catch (MissingRouteException $e) {
             return null;
         }
     }

tests/TestCase/Routing/RouterTest.php

@@ -139,7 +139,7 @@ class RouterTest extends TestCase
         Router::connect('/:controller/:action', ['controller' => 'posts']);
         $this->assertEquals(Router::urlOrNull(['action' => 'view']), '/view');
 
-        $this->assertEquals(Router::urlOrNull(['action' => 'view', 'controller' => 'users', 'plugin' => 'test']), null);
+        $this->assertNull(Router::urlOrNull(['action' => 'view', 'controller' => 'users', 'plugin' => 'test']));
     }
 
     /**