mocking interfaces in php

IInputConfigRepositoryTest.php

<?php
namespace Test\Unit\Domain\Repositories;
use Domain\Repositories;
use Domain\Entities\InputConfig;
use Infrastructure\Reflection\Reflection;
class IInputConfigRepositoryTest extends  \PHPUnit_Framework_TestCase
{
    public function setUp() {
        $this->mock = $this->getMockBuilder('Domain\Repositories\IInputConfigRepository')
            ->disableOriginalConstructor()
            ->getMock();
    }

    public function tearDown() {
        $this->mock = null;
    }

    public function testFindMethod() {

        $return = new InputConfig();
        Reflection::setProtectedVar($return,'input_num',1);

        $this->mock->expects($this->any())
            ->method('find')
            ->with($this->equalTo(1))
            ->will($this->returnValue($return));

        $this->assertEquals(1,$this->mock->find(1)->getInputNum());
    }
}