[6.x] aliasMiddleware doesn't work in test mode if 'router' overriden

[imanghafoori1]

• Laravel Version: 6.0.4
• PHP Version: 7.3

Description:

if we register our middlewares from a service provider like this: app('router')->aliasMiddleware( 'myNiftyMiddleware', ... );;
and we also override the 'router' on the container:

    $router = new SpyRouter(app('events'), app());
    $this->app->singleton('router', function ($app) use ($router) {
         return $router;
    });
    Route::swap($router);

everything is ok in a normal web request, but when we run tests it throws the error:

Illuminate\Contracts\Container\BindingResolutionException: Target class [myNiftyMiddleware] does not exist.

I discovered it while the laravel-microscope was installed (which overrides the router with a sub-class of it) and middlewares were registered by aliasMiddleware from a service provider.
So if any package is installed on a project which overrides the default core router
and user-space code uses aliasMiddleware() to register middlewares. (in case they want to create a package or create a modular application)
The tests can not be run on the endpoints which has that particular middleware on the way.

All and all, it is not severe and does not affect production at all.
but for modular architectures, this may become a headache.

[driesvints]

Moving to discussions.

[imanghafoori1]

let me note that if we do the binding slightly different like below, it would fail again:

<?php
public function register () {
     $this->app->singleton('router', function ($app) {
          return new SpyRouter(app('events'), app());
     });
     Route::swap($this->app->make('router'));
}