Right now, no tool can show you code coverage live while you are stepping through your code in Visual Studio’s debugger. Most coverage tools only work after you run unit tests or run the app separately. For example, Visual Studio’s built-in coverage and Fine Code Coverage need tests, and OpenCover needs you to run your program outside the debugger. JetBrains dotCover can measure coverage when you run the app (not just tests), but it doesn’t update coverage while you are stepping through code. So, there isn’t a tool that shows coverage in real-time during debugging yet.