Mocking a static method with Mockery

Code
<?php

use Zend\Stdlib\ArrayUtils;

/**
 * The class to test
 */
class Foo
{
    public function 
mergeAndFoo($array1$array2)
    {
        
$merged ArrayUtils::merge($array1$array2);
        
$merged[] = 'foo';
        
        return 
$merged;
    }
}

class 
Static2Test extends PHPUnit_Framework_TestCase
{
    public function 
testMergeAndFoo()
    {
        
$mock Mockery::mock('alias:' ArrayUtils::CLASS);
        
$mock->shouldReceive('merge')
            ->
andReturn([]);
        
        
$array1 = ['bar''baz'];
        
$array2 = [100200];
        
        
$foo = new Foo();
        
$actual $foo->mergeAndFoo($array1$array2);
        
        
$this->assertEquals(['foo'], $actual);
    }
    
    protected function 
tearDown()
    {
        
Mockery::close();
    }
}
Result
Time: 167 ms, Memory: 2.00MB

OK (1 test, 0 assertions)
Used Versions
PHP 7.1, Zend 3.0, Symfony 3.2, Laravel 5.2, PHPUnit 5.6, Doctrine 2.6