public MapConfig setAsyncBackupCount(int asyncBackupCount) {
        this.asyncBackupCount = checkAsyncBackupCount(backupCount, asyncBackupCount);
        return this;
    }
@Test(expected = IllegalArgumentException.class)
    public void setAsyncBackupCount_whenTooLarge() {
        MapConfig config = new MapConfig();
        // max allowed is 6
        config.setAsyncBackupCount(200);
    }