Behat\Testwork\ServiceContainer\ExtensionManager::validateExtensionInstance PHP Method

    private function validateExtensionInstance($extension, $locator)
    {
        if (null === $extension) {
            throw new ExtensionInitializationException(sprintf('`%s` extension could not be found.', $locator), $locator);
        }
        if (!is_object($extension)) {
            throw new ExtensionInitializationException(sprintf('`%s` extension could not be initialized.', $locator), $locator);
        }
        if (!$extension instanceof Extension) {
            throw new ExtensionInitializationException(sprintf('`%s` extension class should implement Testwork Extension interface.', get_class($extension)), $locator);
        }
    }