Today’s software failures have two dominating root causes: code bugs and misconfigurations. To combat failure-inducing software changes, unified regression testing (URT) is needed to synergistically test the changed code and all changed production configurations (configs) for deployment reliability. However, URT could incur high cost to run a large number of tests under multiple configs. Regression test selection (RTS) can reduce regression testing cost. Unfortunately, no existing RTS technique reasons about code and config changes collectively. We introduce Unified Regression Testing Selection (uRTS) to effectively reduce the cost of URT. uRTS supports project changes on 1) code only, 2) configs only, and 3) both code and configs. It selects regular tests and configuration tests with a unified selection algorithm. The uRTS algorithm analyzes code and config dependencies of each test across runs and across configs. uRTS provides the same safety guarantee as the state-of-the-art RTS while selecting fewer tests and, more importantly, reducing the end-to-end testing time. We implemented uRTS on top of Ekstazi (a RTS tool for code changes) and Ctest (a config testing framework). We evaluate uRTS on hundreds of code revisions and dozens of configs of five large projects. The results show that uRTS reduces the end-to-end testing time, on average, by 3.64X compared to executing all tests and 1.87X compared to a competitive reference solution that directly extends RTS for URT.