Mocking static method calls in PHP

Static method calls are sometimes necessary due to an existing API or because there is no alternative like injectable services. This makes them basically impossible to mock for unit testing.

An example for TYPO3:

/**
 * Trait for static method calls
 *
 * This is useful to make static method calls mockable in tests.
 *
 * This trait must not be used more than once in a class hierarchy,
 * otherwise endless call loops occur for parent method calls.
 * See bugs.php.net/bug.php for details.
 */
trait StaticCalling {
  /**
   * Performs a static method call
   *
   * Note that parent::class should be used instead of 'parent'
   * to refer to the actual parent class.
   *
   * @param string $classAndMethod Name of the class
   * @param string $methodName Name of the method
   * @param mixed $parameter,... Parameters to the method
   * @return mixed
   */
  protected function callStatic($className, $methodName) {
    $parameters = func_get_args();
    $parameters = array_slice($parameters, 2); // Remove $className and $methodName

    return call_user_func_array($className . '::' . $methodName, $parameters);
  }
}

class MyClass {
  use StaticCalling;
  public function foo() {
    $text = $this->callStatic(LocalizationUtility::class, 'translate', 'foo');
    // Do something with $text
  }
}

class MyClassTest extends \PHPUnit_Framework_TestCase {
  /**
   * @test
   */
  public function doesWhatIsExpected() {
    $myClassInstance = $this->getMockBuilder(MyClass::class)
      ->setMethods(['callStatic'])
      ->getMock();

    $myClassInstance
      ->method('callStatic')
      ->with(LocalizationUtility::class, 'translate', 'foo')
      ->willReturn('mocked');
    
    $myClassInstance->doSomething();
  }
}