public static Builder custom() {
        return new Builder();
    }
@Test
    public void builderRefreshPeriodNegative() throws Exception {
        exception.expect(IllegalArgumentException.class);
        exception.expectMessage("RefreshPeriod is too short");
        RateLimiterConfig.custom()
            .timeoutDuration(TIMEOUT)
            .limitRefreshPeriod(Duration.ofNanos(-1))
            .limitForPeriod(LIMIT)
            .build();
    }