Context: The correct selection of a software testing technique can positively influence the quality of the software in development. In previous work, a mapping study was conducted to identify approaches concerning software testing techniques selection, highlighting the attributes used to support the testing technique selection process. Objective: This paper presents a unified catalog composed of testing technique selection attributes, built from the mapping study results. The aim is to assist testing practitioners to choose the best testing techniques to apply to a particular software project. Method: Through the 10 studies that present the attributes used for supporting the process of selecting software testing techniques, 178 attributes were extracted. From this, a careful analysis was conducted to exclude the attributes that appeared duplicated. Results: According to the objective and features, the catalog of attributes was classified into 8 categories, namely (i) general testing characteristics; (ii) tools; (iii) test team; (iv) software project; (v) orthogonal defect classification (ODC) faults; (vi) web applications; (vii) concurrent software; and (viii) model-based testing. Conclusion: Through the development of this catalog, we intend to help testers, guiding them on how to select the best testing technique to be applied to software projects in the industry. It is expected that this work can foster collaboration between industry and academia to help improve the quality of software developed by choosing the best testing technique. Also, we want to further extend this work through the validation in industry real cases.