NUnit is currently built under five different runtimes on Windows – plus two on Linux. Each build is tested under the same runtime on which it was built and on a number of the other runtimes. That’s a lot of TestResult files.
I use nunit-summary.exe to quickly view what happened in a particular run. For example,
nunit-summary TestResult-mono-1.0.xml -noheader -brief
gives me a simple, one-line summary of what happened when I ran my tests under mono-1.0 – the naming convention is built into my build script. The following command gives me a set of files TestResult-net-1.0.txt, TestResult-net-1.1.txt, etc. each containing the summary line as well as any failed or not run tests for the corresponding xml file.
nunit-summary TestResult*.xml -out=*.txt
See the help for the command for other things you can do, including using your own xsl to transform the output.
The nunit-summary program is available on the GitHub.