This dataset contains the code and inputs for running the tests in the working paper "Analyzing Performance and Scalability of Benders Decomposition for Generation and Transmission Expansion Planning Models". This work tests various speedup strategies for solving generation and transmission expansion planning problems using Benders decomposition. These tests are run with an adaptation of the Julia package GenX.jl. The dataset contains a single zip folder: GTEP_Benders_GenX.zip - This zip folder contains a subdirectory called GenX.jl which has the source code for building the respective models with GenX.jl. The test system itself is contained in the GenX.jl/example_systems/12_RTS_Case subdirectory. This subdirectory also contains a Readme with further details on how to run the scripts in this work and how the model is constructed. The GenX.jl subdirectory also serves as a Julia environment that can be activated for running these scripts. The sqlite database in this work was provided by the Sienna team at the National Laboratory of the Rockies. It is constructed to be read in via the PowerSystemsInvestmentsPortfolios package available here.