Many coverage tools evaluate an entire project, including unit test code itself. In VS 2013, the Analyze Code Coverage/All Tests option includes test code in its report. OpenCover does so as well I believe. In Eclipse, a Maven project with the typical src/main/java and src/test/java setup, EclEmma will report coverage for both main and test code
This seems of minimal value to me, except for possibly ensuring that all tests are actually being executed. With test code included, the coverage % is often artificially high since often the tool will report close to 100% coverage for test code, which can skew the entire project above a benchmark level (say 80%) that it might not have otherwise achieved.
Are there legitimate reasons to include test code in coverage? Or should I continue filtering it out when automating our coverage reporting?