Explore testing strategies for complex logic in a Scala Days conference talk. Dive into example-based, property-based, and mutation testing techniques. Learn how to detect and create mutants, traverse trees, and define mutations. Discover the "spellbook" for summoning mutants and running experiments using sbt. Examine HTML reports, performance considerations, and mutation switching. Gain insights into usage patterns, non-compiling mutants, and future ideas for testing in Scala. Equip yourself with advanced testing knowledge to ensure robust code quality in complex systems.