customerSession = $this->getMockBuilder(\Magento\Customer\Model\Session::class) ->disableOriginalConstructor() ->setMethods(['setWishlistItemCount', 'isLoggedIn', 'getCustomerId']) ->getMock(); $this->observer = new Observer( $this->customerSession ); } public function testExecute() { $event = $this->getMockBuilder(\Magento\Framework\Event\Observer::class) ->disableOriginalConstructor() ->getMock(); /** @var $event \Magento\Framework\Event\Observer */ $this->customerSession->expects($this->once()) ->method('setWishlistItemCount') ->with($this->equalTo(0)); $this->observer->execute($event); } }