Dataset for the master dissertation "How and Why Python Developers Migrate to Pytest". The `10_systems` zip file contains the aggregated and intermediate files for the systems used for precision and recall analysis. The `top_100_systems` zip file contains the aggregated and intermediate files for the top 100 python systems analyzes. The `rq5_*` files contain data to assess the advantages and disadvantages found in 100 issues or pull requests and in the Grey Literature Review. The columns indicate if the advantages (A) or disadvantages (D) are present or not. Lastly, the `rq6_*` files present a similar structure, with themes defined while performing a thematic analysis for qualitative research questions.