For my work I usually write an unit test and want to execute this test immediatelly to see whether and how it passes. If an application has many, many tests running them all would slow me down and disrupt the flow. To deal with this I once wrote small test library which checks timestamps of source files containing tests and runs only tests from recently modified files. (In my case I run tests from files changed during last 10 mins when the application starts.) This way I am able to write a test and run it within mere second(s). Perhaps similar functionality could be considered into Boost.Test (I didn't find it here). The implementation is portable, it uses only __FILE__, stat() and time(). It may be possible to check also source file dependencies for changes (up to some point) but I do not do it and it is not obstacle for me. Syntax I use looks like TEST { ... assert(...); // assert breaks into debugger } .. run_recently_modified_tests() /Pavel