TestColumnSeeking is mathematically bound to fail

First I'd like to say that TestColumnSeeking is a bad test. It's not documented, it's non-deterministic, it's 2 methods with almost the same code.

So in each test it populates column lists this way:

    for (int i = 0; i < numberOfTests; i++) {
      kvMaps[i] = new HashMap<String, KeyValue>();
      columnLists[i] = new ArrayList<String>();
      for (String column : allColumns) {
        if (Math.random() < selectPercent) {
          columnLists[i].add(column);
        }
      }
    }

Since selectPercent is 50% and there are 10 columns, there's something like a 1/1024 chance that one of the column list ends up with 0 column. This is later mismanaged in the checks. First something like this will be printed out:

2013-01-28 11:50:02,200 INFO [pool-1-thread-1] regionserver.TestColumnSeeking(140): Columns: 0 Keys: 0

Like it says, there's 0 columns so it couldn't add data. But then it still makes sure later that the data is there with this check:

assertEquals(kvSet.size(), results.size());

Do notice that the parameters are reversed, and here the results.size() will be 0 since there are 0 columns for this test.

I see multiple ways to fix this:

• Skip tests that have 0 columns
• Change the randomness to at least have 1 column (like select 1 + 0..9 columns)
• Redo the whole unit test to not rely on randomness