TC MA wrote:

After bjam is executed, both .output and .run files are executed. However, they are the same in content. Why not just use one file, why need both .output and .run files?

Because presense of the '.run' file indicates the the test succeeded, and enables bjam to avoid rerunning the test again. If test fails, .run is not created. .output is still created in case you want to look at the output and diagnose the problem. BTW, it's suggested to use full names, not nicknames on Boost mailing lists. - Volodya