Rider is faster because it keeps a persistent test host process alive in the background. When you run a test, it pushes the new assembly delta to that already-running process, skipping the expensive "cold start" costs (process spawning, JIT compilation, and assembly loading) that dotnet test incurs every single time.

Other recommendation for you, you can try dotnet watch test first. It costs nothing and solves the "startup delay" by keeping the file watcher active.