What did they do in IEA 34/43? Or how to diagnose and repair bugs in 500,000 lines of code

This paper presents an overview of the recently completed International Energy Agency Solar Heating and Cooling Task 34 and Energy Conservation in Buildings and Community Systems Annex 43 (IEA 34/43) on Testing and Validation of Building Energy Simulation Tools. The paper includes discussion of the technical and historical context, methodology, organization, accomplishments, and adoption by standards organizations and other regulatory entities.