php - Laravel Mockery - Mocking a class with dependencies injected into constructor -

i trying mock class it's own constructor dependencies. using laravel 5.2.

class {     public function something() {} }      class b {   protected $a;   public function __construct(a $a) {     $this->a = $a;   }    public function geta() {     return $this->a->something();   } }  mockingtest extends testcase {    public function testitgetssomething() {     $m = mockery::mock('b');     $m->shouldreceive('geta')->once()->andreturn('something');   } } 

i aware can change classb.__construct(a $a) to:

  public function __construct(a $a = null) {     $this->a = $a ?: new a();   } 

but there better / cleaner way of doing this? don't want change constructor code sake of unit testing if there more acceptable method.

i'm not 100% sure want test, if want mock class instance within b class can inject mocked version of when creating new instance of b:

$mocka = mockery::mock('a'); $mocka->shouldreceive('something')->once()->andreturn('something');  $classbwithmockeda = new b($mocka); 

then can instance (if want test geta-method within b class):

$this->assertequals('something', $classbwithmockeda->geta());