VS 2010, NUNit, and “The breakpoint will not currently be hit. No symbols have been loaded for this document”

There’s another similar question here on Stack Overflow, where I posted my answer with what worked for me. I can set breakpoints and start NUnit directly from Visual Studio 2010 with Debug -> Start New Instance (which I think is your goal).

I set nunit.exe as the external program in project -> Properties -> Debugging and added:

<startup>
    <requiredRuntime version="4.0.30319" />
</startup>

to the nunit.exe.config file found next to the nunit executable in the NUnit install directory.