Routing by Domain via Domains in Database

I need to route domains dynamically by domains pulled from my database. My current setup looks like this:

// domain handler
Route::domain('{userDomain}', function(){
    Route::get('{fullPath}', function($domain, $fullPath){
           // If the domain in the database handle it with the $fullPath
    })
        ->where('fullPath', '.*');
});

// Typical app routes
Route::get('/', ...)
Route::get('/home', ...)

The problem that I am encountering is that my "typical" app routes and "domain-handled" routes conflict with one another. For example, the domain-handled routes may have a path of / which is also used by my homepage making handled-domain.com/ conflict with myapp.com/.

I thought I had this fixed by creating a middleware and adding this to my RouteServiceProvider::map():

    /**
     * Define the routes for the application.
     *
     * @param  \Illuminate\Routing\Router  $router
     * @return void
     */
    public function map(Router $router)
    {
	if(!$this->isMainAppDomain()) {
            $this->mapVanityRoutes($router);
            return;
        }

        $this->mapWebRoutes($router);

        $this->mapApiRoutes($router);

        //
    }

The problem with this is that it is incompatible with tests. It seems the app is initiated with my APP_URL (main app URL) and in tests $this->refreshApplication() does not help.

In short, how do I route by domains in my database and prevent and prevent my main app routes from conflicting with these requests?

P.S. I tried Route::domain on my main app URLs, but this doesn't impact routes generated for the web middleware by vendors.