Definition:
PSR testing is Performance, Stability, Reliability with Scalability i.e How fast? How long? How often and How much? As long as the awareness is there and the organization is seriously asking those questions with everything they develop then PSR is successfully integrated into a team.
PSR capability is two phased scalability testing approach to identify bottlenecks and then identifying baseline, comprehensive test reports and root cause analysis, tuning of code and other application parameters, capacity planning based on the test results. Detailed reporting based on impact analysis.
Further Reading:
Book: AGILE TESTING A Practical Guide for Testers and Agile Teams