Trying to set expectations for a cloned object in PHP

Running test.php

phpunit --debug test.php 
PHPUnit 3.5.13 by Sebastian Bergmann.


Starting test 'Cloner_Test::testFunctionThatClones'.
F

Time: 1 second, Memory: 6.50Mb

There was 1 failure:

1) Cloner_Test::testFunctionThatClones
Expectation failed for method name is equal to <string:__clone> when invoked 1 time(s).
Method was expected to be called 1 times, actually called 0 times.


FAILURES!
Tests: 1, Assertions: 1, Failures: 1.

test.php

<?php

// Load PHPUnit out of our include path (e.g. from a PEAR install)
include 'PHPUnit/Autoload.php';

class Clonable
{

    public function functionOnClonable()
    {
    }

}

// This is our system under test
class Cloner
{

    public function functionThatClones(Clonable $clonable)
    {
        $clone = clone $clonable;
        $clone->functionOnClonable();
    }
}

class Cloner_Test extends PHPUnit_Framework_TestCase
{

    public function testFunctionThatClones()
    {
        $cloner = new Cloner(); // system under test
        $mockClonable = $this->getMockBuilder('Clonable')
                             ->getMock();
        $mockClone = $this->getMockBuilder('Clonable')
                          ->getMock();
        // Try to return $mockClone when functionThatClones
        // clones our mock Clonable
        $mockClonable->expects($this->once())
                     ->method('__clone')
                     ->will($this->returnValue($mockClone));
        $mockClone->expects($this->once())
                  ->method('functionOnClonable');
        $cloner->functionThatClones($mockClonable);
    }

}