Why does unitils-dbunit have different records?

Question

I need to access 2 dbs, so I have to use the version 3.4.

I defined 2 xml files to stored the test data, and put the @Dateset on class, likes:

@Test
@DataSets({
    @DataSet(value = "testdb1.xml", databaseName="db1"),
    @DataSet(value = "testdb2.xml", databaseName="db2")})
public class DbTestTest {

and in my test method, the DAO would access the database tables, the table records should from the "testdb1.xml"/"testdb2.xml". Because the test data is fixed, so DAO should return same records every time, so it can make sure the assert as true. But sometimes the records is expect, sometimes is not. So, my assert will failed.

To run unit tests, I have 2 ways:
1, run in IDE(Eclipse), always passed
2, run in "mvn clean install", would occurs the problem as my said

Besides, I found the "delete from mytable" sql occurred many times, why not 1 time?

I don't know why. Any ideas? Thanks in advance!

unitils-dbunit version: 3.4.2
db: postgresql 9.6.5 && 10.4