Keep the mapping logic and the testing logic separate. Do not copy formulas from the PowerCenter mapping into the data validation test. If the mapping logic contains errors, the test result will replicate the mapping error. Remember that Data Validation Option validates data, but it does not validate the mapping logic.
Perform simple tests first, such as counts and constraint checks, to identify obvious errors that might be easy to fix.
Consider splitting complex SQL into more than one table pair object.
You do not have to perform all testing with Data Validation Option. You might want to perform a particular step with SQL.