Context: Software Product Line Engineering (SPLE) has emerged as a thriving approach for software products constructions. In SPLE, a triumphant software product is highly reliant on the validity of an SPLE. Hence, validation is a significant process within SPLE. Objective: In this paper, we reviewed the related works in the area of automated validation of SPLE to bring to light the pros and cons of the related works and suggest the future directions in this research area. Method: We started by defining the validation operations followed by classification of the related works in eight groups based on the technique or method that is used. The general attributes of each class are highlighted and the main strengths and weaknesses of each class related to the validation of SPLE are thrashed out. Subsequently, we analyzed each work to find out which validation operations are achieved and how they are satisfied. Finally, we abridged the current situation and recommended how the validation of SPLE can be enhanced in each operation.

Results: The research gap in the area of validation of SPLE has been clarified by recommending the future directions.

Conclusion: It is concluded that some works cannot gratify all the validation operations because the technique or method used has its weaknesses that prevented the completion of the validation process. Moreover, we conclude that this area of research has room for improvement by validating the domainengineering directly instead of validating software products during the configuration process.