This comprehensive TECDOC on the International Project on Development of an Approach for Defining Generic Test Conditions for Dual Purpose Casks (GeTeC) addresses the growing need for efficient and safe spent fuel storage solutions. As reactor pool capacities reach their limits, the innovative Dual Purpose Cask (DPC) concept offers a flexible and economically efficient option for managing spent fuel. DPCs are designed to meet stringent national and international safety standards, ensuring safe storage and transport without the need for additional equipment. The IAEA's GeTeC working group has developed an integrated safety case methodology for DPCs, providing Member States with a robust framework to establish their national requirements. This publication outlines generic test conditions for DPCs, reflecting the latest industry standards and best practices.