Testing in Data World

Management tries to make decisions based on numbers and objective data, not just gut feeling. How to test the software that was used to calculate these numbers? Your code processed company information for the whole year and gave answer: 42%. Is it correct answer or there is a bug and 43% is what we should get? Based on real experience from Analytics department of Toptal I would try to answer these questions. BI, ETL, DWH, ML… If you know these abbreviations - welcome to talk about testing in data world.