public synchronized void loadInitial() {
        Collection<Mapper> mappers = NacosServiceLoader.load(Mapper.class);
        for (Mapper mapper : mappers) {
            putMapper(mapper);
            LOGGER.info("[MapperManager] Load Mapper({}) datasource({}) tableName({}) successfully.",
                    mapper.getClass(), mapper.getDataSource(), mapper.getTableName());
        }
    }
@Test
    void testLoadInitial() throws NoSuchFieldException, IllegalAccessException {
        MapperManager instance = MapperManager.instance(false);
        instance.loadInitial();
        Class<MapperManager> mapperManagerClass = MapperManager.class;
        Field declaredField = mapperManagerClass.getDeclaredField("MAPPER_SPI_MAP");
        declaredField.setAccessible(true);
        Map<String, Map<String, Mapper>> map = (Map<String, Map<String, Mapper>>) declaredField.get(instance);
        assertEquals(2, map.size());
    }