private static Class<?>[] getAnnotatedClasses(Class<?> klass) throws InitializationError {
        SuiteClasses annotation= klass.getAnnotation(SuiteClasses.class);
        if (annotation == null) {
            throw new InitializationError(String.format("class '%s' must have a SuiteClasses annotation", klass.getName()));
        }
        return annotation.value();
    }