We use the xUnit plugin to parse Unittest++ output files. On many of our projects, the number of tests reported in Jenkins fluctuates from build to build. I have verified that all our test output files are properly converted to jUnit test files, but either the plugin does not report them correctly to Jenkins or something is up in Jenkins itself.

Not sure exactly what is needed to diagnose this - many of the data we have in our Jenkins is internal and cannot be shared, but if I can help with something I will.