php - Laravel Unit Testing Dependency Injection -

i'm trying write test class shopping cart. here have:

shoppingcarttest.php

class shoppingcarttest extends testcase {      use databasetransactions;      protected $shoppingcart;      public function __construct() {         $this->shoppingcart = resolve('app\classes\billing\shoppingcart');     }      /** @test */     public function a_product_can_be_added_to_and_retrieved_from_the_shopping_cart() {          // placeholder @ moment         $this->asserttrue(true);     }  } 

however, when run phpunit, seems laravel unable resolve shoppingcartclass.

here error:

fatal error: uncaught exception 'illuminate\contracts\container\bindingresolutionexception' message 'unresolvable dependency resolving [parameter #0 [ <required> $app ]] in class illuminate\support\manager' in c:\development server\easyphp-devserver-16.1\eds-www\nrponline\vendor\laravel\framework\src\illuminate\container\container.php:850 

i have shoppingcart class being resolved in number of different controllers fine.

why can't laravel resolve during tests?

i refered this post still didn't have luck.

i figured out. here updated class.

class shoppingcarttest extends testcase {      use databasetransactions;      protected $shoppingcart;      public function setup() {          parent::setup();          $this->shoppingcart = $this->app->make('app\classes\billing\shoppingcart');     }      /** @test */     public function a_product_can_be_added_to_and_retrieved_from_the_shopping_cart() {          // placeholder @ moment         $this->asserttrue(true);     }  } 

thanks @edcs guiding me in right direction. need use setup function , not __construct app instance hasn't been created yet.