test helper for private methods

test_helper_for_private_methods.php

<?php

namespace xxx\Tests;

class Helper
{
    public static function invokePrivateMethod(&$object, $methodName, array $parameters = array())
    {
        $reflection = new \ReflectionClass(get_class($object));
        $method = $reflection->getMethod($methodName);
        $method->setAccessible(true);
        return $method->invokeArgs($object, $parameters);
    }

    public static function getPrivateProperty(&$object, $propertyName)
    {
        $reflection = new \ReflectionClass(get_class($object));
        $reflectionProperty = $reflection->getProperty($propertyName);
        $reflectionProperty->setAccessible(true);
        return $reflectionProperty->getValue($object);
    }

    public static function setPrivateProperty(&$object, $propertyName, $value)
    {
        $reflection = new \ReflectionClass(get_class($object));
        $reflectionProperty = $reflection->getProperty($propertyName);
        $reflectionProperty->setAccessible(true);
        $reflectionProperty->setValue($object, $value);
    }
}

usage_of_the_test_helper.php

<?php

namespace xxx\Tests\Unit\yyy;
use xxx\Tests\TestCase;
use xxx\Tests\Helper;
use xxx\SomeClass;

class yyyTest extends TestCase
{
    /**
     * @test
     */
    public function cacheKeyIds()
    {
        $someInstance = new SomeClass();
        $resultOfPrivateMethod = Helper::invokePrivateMethod($someInstance, 'nameOfThePrivateMethod', [
            'param1',
            'param2'
        ]);
        $this->assertEquals('the expected result', $resultOfPrivateMethod);
    }
  
    // ...
}