I'll answer my own question since I've done some more research.  The trace.py module in Python's standard library doesn't know how to create a module name for modules loaded from locations other than sys.path.  It tries to use the full file path, but on Windows, that starts with "<drive>:", and ":" isn't a valid part of a filename. <a href="http://bugs.python.org/issue4943">http://bugs.python.org/issue4943</a> Matt <div class="gmail_quote">On Sat, Jan 3, 2009 at 2:19 PM, Matt McClure <<a href="mailto:mlm@aya.yale.edu">mlm@aya.yale.edu</a>> wrote: <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">I'm using 'bzr --coverage coverdir selftest' for the first time, and I hoped it would give me test coverage information for my bzrp4 plugin.  However, I don't see any .cover files in coverdir for bzrp4 source files.  I used BZR_PLUGIN_PATH to set the parent directory of the bzrp4 directory.  I do see .cover files for bzr source files and for the launchpad plugin that is installed inside the bzrlib/plugins directory. How can I make --coverage find my plugin source files relative to BZR_PLUGIN_PATH?  Or is there a better way to get coverage information for Bazaar plugins? Thanks, Matt </blockquote></div>