Hey, we can't think of everything :^). NUnit takes only 1 to 3 command-line parameters (see
http://nunit.org/commandLine.html), so it should be pretty simple to create a Run Program step for it. Console apps typically return a non-zero exitcode on failure (hopefully Nunit does too), so you shouldn't need to parse the output, since the Run Program action will fail on a non-zero exitcode.