public CardinalityEstimatorConfig setAsyncBackupCount(int asyncBackupCount) {
        this.asyncBackupCount = checkAsyncBackupCount(backupCount, asyncBackupCount);
        return this;
    }
@Test(expected = IllegalArgumentException.class)
    public void testSetAsyncBackupCount_withNegativeValue() {
        config.setAsyncBackupCount(-1);
    }