What do you get with --verbose? It almost sounds like it's picking up your user-config.jam, but --test-config should override the default configuration files.
When I run: python zlib.py --verbose msvc > out.txt I get this: error: at Jamroot.jam:3 error: zlib is already configured failure {{{ "['c:\\boost\\tools\\build\\v2\\test\\../engine\\bin.ntx86\\bjam', '-sBOOST_BUILD_PATH="c:\\boost\\tools\\build\\v2\\test/.."', '-d+2', 'toolset=mock', '--test-config="c:\\boost\\tools\\build\\v2\\test\\test-config.jam"', '--ignore-toolset-requirements']" returned 1 }}} reason {{{ unexpected status returned by bjam }}} changes caused by the last build command {{{ Added files : [] Removed files : [] Modified files: [] Touched files : [] }}} STDOUT {{{ error: at Jamroot.jam:3 error: zlib is already configured }}} STDERR {{{ }}} stacktrace {{{ at line 590 of c:\boost\tools\build\v2\test\BoostBuild.py (fail_test) from line 485 of c:\boost\tools\build\v2\test\BoostBuild.py (run_build_system) from line 32 of zlib.py (<module>) }}} Christian