long elapsed = endTime - startTime;
        assertTrue("Expected minimal sleep time with negative interval, got " + elapsed + "ms", elapsed < 50);
    }

    @Test
    public void test_update_callsLoad() throws InterruptedException {
        CountDownLatch latch = new CountDownLatch(1);
        configHelper.setLoadCallback(() -> {
            latch.countDown();
            return 1;
        });