@Test
public void testToDb() throws SchemaException, MapperException {

    LOG.info("testToDb");
    List<?> db;
    Collection<String> mem = null;
    db = mapper.toDb(mem);
    Assert.assertTrue(db != null);
    Assert.assertTrue(db.isEmpty());
    mem = new ArrayList<>();
    db = mapper.toDb(mem);
    Assert.assertTrue(db != null);
    Assert.assertTrue(db.isEmpty());
    mem.add("silver");
    db = mapper.toDb(mem);
    Assert.assertTrue(db != null);
    Assert.assertTrue(db.size() == 1);
    Assert.assertEquals("silver", db.get(0));
    mem.add("gold");
    db = mapper.toDb(mem);
    Assert.assertTrue(db != null);
    Assert.assertTrue(db.size() == 2);
    Assert.assertEquals("gold", db.get(1));
}