Discover how you can test your code much more thoroughly than just running "make check", but with very little more effort. The buildfarm client automates thorough testing of new code as well as committed code. For many years the buildfarm client has had an offline mode that will test a given local codebase rather than pulling from git. Some recent enhancements in the client have made this mode more usable by developers and committers. Now it's very easy to reduce very substantially the chances that the code you're developing or committing will send the whole buildfarm red. The talk will describe in detail the whole battery of tests the client runs, and how to use offline mode effectively as part of your development and review process. We will show how to keep several configurations for different sorts of tests. We'll see how to run valgrind to check for memory leaks without touching the core code at all. And we'll show how to add a module to test non-core code such as an extension.