@Override
    public Optional<Decision> onMemoryUsageChanged(
            int numTotalRequestedBuffers, int currentPoolSize) {
        return numTotalRequestedBuffers < currentPoolSize * releaseThreshold
                ? Optional.of(Decision.NO_ACTION)
                : Optional.empty();
    }
@Test
    void testOnUsedMemoryBelowThreshold() {
        Optional<Decision> memoryUsageChangedDecision = spillStrategy.onMemoryUsageChanged(5, 10);
        assertThat(memoryUsageChangedDecision).hasValue(Decision.NO_ACTION);
    }