A tester generally does the following task in ETL environment:

1. Review the requirements

2. Review the source data - data profiling.

3. Modify the source data to meet any requirements that

weren't already met with the original source data.

4. Execute the ETL job(s)/transformation(s).

5. Validate the results.

6. Validate that the data is usable. If the data isn't

usable, then you really haven't gained anything.