无法运行phpunit测试，无法打开所需的类

So, here is the strucuture of my project

project_name
  /classes
      Calculator.php
  /test
      CalculatorTest.php
  /vendor
      // Related composer/phpunit etc ... stuff
  composer.json
  composer.lock

Calculator.php

<?php
class Calculator{
    public function double($input){
        return $input * 2; 
    }
}

CalculatorTest.php

<?php

require_once '../classes/Calculator.php'; 

class CalculatorTest extends PHPUnit_Framework_TestCase{

    public $testClass; 

    public function setUp(){
        $testClass = new Calculator; 
    }

    public function testDouble(){
        $result = $testClass->double(2); 
        $this->assertEquals(4, $result);        
    }

}

When I run phpunit ../../test, I get the following error:

Warning: require_once(../classes/Calculator.php): failed to open stream: No such file or directory in C:\wamp\www\phpunit\test\CalculatorTest.php on line 3

Fatal error: require_once(): Failed opening required '../classes/Calculator.php' (include_path='.;C:\php\pear') in C:\wamp\www\phpunit\test\CalculatorTest.php on line 3

I can't find a fix. Do you have any idea?

EDIT
Got, it, forget the spl_autoload_register within the tests classes:

spl_autoload_register(function ($class) {
    require_once 'classes/' . $class . '.php'; 
}); 

You're opening the file in a different page. So the path is incorrect.

try this:

 require_once dirname(__FILE__) . '/classes/Calculator.php

And if Calculator is in the same folder as classes as calculator test than you dont need to set the path /classes