To become a DevOps Engineer, especially if you're from the Automation Testing domain, then you must acquire several technical and soft skills as listed below:
Working experience in storage and network
Gain proficiency in Automation tools
Understand and acquire work experience in cloud and virtualization techniques
Learning and implementing security techniques
Master infrastructure management, compliance, and other tools
Acquire soft skills like good communication, problem-solving, analytical thinking, etc.
These skills will help you become a qualified DevOps Engineer and help you achieve a career transition from the Automation Testing domain. If you aspire to such a career transition, I recommend you enroll in this DevOps Masters Course. Also, watch this video wherein a Software Tester has successfully transitioned to a DevOps career.