DbUnit and nullable columns

We use DbUnit for our database integration tests and this works very well allowing us to populate the database with test data specific for the test at hand.

I have had a problem for the last few hours that has driven me to distraction. I was populating a table with a row and the tests using this data were all OK.

I then added an extra row that also wanted to populate an extra nullable column. The test failed because the test thought this column was null. I stopped the test in the debugger and yes the code was correct, the column was null. What could be wrong ?

My DbUnit XML looked like this:

<dataset>
  <MY_TABLE
      ID="1"
      MANDATORY_COL="This column must have data"
   />

   <MY_TABLE
      ID="2"
      MANDATORY_COL="This column must have data"
      NULLABLE_COL="This column is nullable"
   />
</dataset>

The problem appears to be that DbUnit builds its list of columns from the first occurrance of each table. Any optional columns listed in subsequent entries are simply ignored.

There are two solutions. Either reverse the order of the two items in the XML file, or set the column to null in the rows where the nullable column is not required.