private int getRetentionDays() {
        String val = EnvUtil.getProperty("nacos.config.retention.days");
        if (null == val) {
            return retentionDays;
        }
        
        int tmp = 0;
        try {
            tmp = Integer.parseInt(val);
            if (tmp > 0) {
                retentionDays = tmp;
            }
        } catch (NumberFormatException nfe) {
            FATAL_LOG.error("read nacos.config.retention.days wrong", nfe);
        }
        
        return retentionDays;
    }
@Test
    public void testGetRetentionDays() throws Exception {
        Method method = DefaultHistoryConfigCleaner.class.getDeclaredMethod("getRetentionDays");
        method.setAccessible(true);
        envUtilMockedStatic.when(() -> EnvUtil.getProperty("nacos.config.retention.days")).thenReturn("-1");
        assertEquals((int) method.invoke(defaultHistoryConfigCleaner), 30);
        
        envUtilMockedStatic.when(() -> EnvUtil.getProperty("nacos.config.retention.days")).thenReturn("30");
        assertEquals((int) method.invoke(defaultHistoryConfigCleaner), 30);
        
        envUtilMockedStatic.when(() -> EnvUtil.getProperty("nacos.config.retention.days")).thenReturn("1");
        assertEquals((int) method.invoke(defaultHistoryConfigCleaner), 1);
    }