In this talk I will motivate the need for better testing tools for distributed and concurrent systems. The first part of the talk will describe recent advancements and successes in testing of distributed and concurrent systems. The second part of my talk will then present the design and implementation of dBug - a tool for systematic evaluation of distributed and concurrent systems. The talk will conclude with an overview of two case studies for the use of dBug: the Parallel Virtual File System and FAWN-KV, a distributed key-value storage based on the FAWN architecture.